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There is no Next Episode of ThunderCats planned.
A distant planet is collapsing and about to explode. The Thundercats (Thunderian nobles) and the rest of the Thunderian commoners must find a new home just after their home planet, Thundera, explodes. The Thundercats flagship had already safely left and is now travelling in outer space when an enemy known as the Mutants attack and leaves their ship severely crippled. A young boy named Lion-O must learn what it means to become a man and Lord of the ThunderCats as he learns to wield the power of the Sword of Omens.
Accompanied by the Nobles of Thundera, the leader of the ThunderCats Jaga, and his nurse maid, Snarf, Lion-O escapes the the planet's destruction. After acquiring the Sword of Omens, the ship is attacked by mutants from their home world. During the battle, the Mutants try to get onto the ThunderCats' ship to take the Eye of Thundera, a powerful relic that is passed down from generation to generation of leaders of the ThunderCats. Little do the mutants know, the Nobles are willing to die for their leader and the Eye of Thundera.
The Mutants are beaten back, but with a cost to the ThunderCats: Jaga is left to pilot the ship due to a short to the navigation system (autopilot was normally used when flying at lightspeed) while it is in hyperspace. While the rest are in age-slowing sleep chambers , he makes do with what he can, and sets the ship on autopilot when he is no longer able to pilot it. He programs the computers to wake the remaining ThunderCats when they are about to arrive at the planet, and sets the ship on a crash course for the world that will be known as Third Earth.
There again, the ThunderCats must face some of their old enemies, the Mutants, led by Slithe and, due to surprise of all, Lion-O is now a grown-up ThunderCat. His sleep-chamber was damaged and he grew many years older while the others remained in suspended animation. He is now no longer a Thunderkitten and instead, is in an alien adult body like the nobles he must now lead in battle.
The ThunderCats are busy trying to salvage as much equipment and food rations as they can from the wreck of their fallen spaceship. Panthro, while initially angry that most of their equipment has been destroyed, is confident that enough Thundrillium is left to build a ThunderTank. Lion-O decides to scout the surrounding area, taking the Sword of Omens and Claw Shield with him while Tygra and Cheetara go searching for a suitable location to build Cats Lair.
Meanwhile, the Mutants, while searching for the ThunderCats as well as a suitable location to build Castle Plun-Darr, come across an old pyramid. As they approach the pyramid, it starts to emit lightning, forcing the Mutants to land their ship. Inside the pyramid, Mumm-Ra emerges and offers the Mutants a chance to ally with him to obtain the Eye of Thundera. At first the Mutants reject his offer and threaten to blow up Mumm-Ra's pyramid. Mumm-Ra in turn retaliates by sinking their spaceship where it stands. The Mutants, now weaponless without their ship, have no choice but to join forces with him. He teleports them to the woods where Lion-O is scouting alone.
The Mutants re-materialize in the woods and ambush Lion-O but he manages to call for help using the Sword of Omens and Panthro, Wilykit and Wilykat arrive to rescue him. Defeated by the ThunderCats, the Mutants teleport back to Mumm-Ra's pyramid. Lion-O, surprised as to why Tygra and Cheetara did not see the Cat signal, goes off in search of them.
Back inside the Black Pyramid, Mumm-Ra ridicules the Mutants for failing miserably to obtain the Sword from Lion-O. The Mutants retort by taunting Mumm-Ra which greatly angers him and he decides to show them his true power by transforming into his Ever-living form and flying out of his pyramid.
While searching for Tygra and Cheetara, Lion-O comes across a strange black lake which is filled with thick, hot, bubbling black ooze. Mumm-Ra suddenly appears and a fight ensues between him and the young lord. The Sword is knocked from Lion-O's hands and falls into the black lake. Lion-O retrieves it and tries to call the other ThunderCats, but the Eye of Thundera, now covered by the black ooze, does not respond. Mumm-Ra manages to pin down Lion-O and in a desperate attempt to shield himself from the fiend, Lion-O holds up his Claw Shield in defense. Mumm-Ra, upon seeing his reflection in the Claw Shield, is horrified and driven back to his pyramid.
Panthro has completed building a ThunderTank using only the equipment that he salvaged from their wrecked spaceship. Suddenly a hail storm begins and Tygra , Cheetara , Wilykit and Wilykat take refuge inside the spaceship wreck while Panthro opts to stay inside the tank. The storm completely buries the ship in debris but Panthro manages to dig it out using the tank.
Meanwhile, Lion-O and Snarf are exploring the surrounding woods when Lion-O falls into a trap hole in the ground. The creatures responsible for setting the trap are a group of robotic teddy bears who tie-up both Lion-O and Snarf and take them to their village . Once there, the leader of the bears, Ro-Bear Bill, unties the two captives and tells them that they are a race called Berbils who, just like the ThunderCats, are aliens here on Third Earth, having come from the planet Ro-Bear.
He then takes the two guests around a tour of their village but it is cut short by the sound of an alram, signalling the impending attack by creatures known as Trollogs . Ro-Bear Bill explains to Lion-O that the Trollogs frequently raid their village for their Berbil Fruit which they in turn give to the Giantors in exchange for the fruits of the Trollberry bushes, the Trollog's only diet. Lion-O scares of off the Trollogs using the Sword of Omens but soon the furious Giantors arrive. However, Lion-O calls the other ThunderCats for help who arrive swiftly and drive off the Giantors. This act of helping the Berbils further strengthens the friendship between the two alien groups.
Mumm-ra meanwhile, having witnessed all the events from his Cauldron, is enraged at the new alliance as it would mean an endless food supply for the ThunderCats from the Berbil Village. He assumes the form of a swarm of locust and attacks the Berbil Village. As soon as Lion-O interferes, the swarm combines into one giant locust. Lion-O jumps onto the huge insect and forces it away from the village. However, the giant locust drops Lion-O into the crater of a nearby volcano and as he is falling, the Sword of Omens falls out from the Claw Shield. At this point, the spirit of Jaga appears and tells Lion-O that he can call to the Sword and it will obey. Lion-O summons the Sword to his hand and it carries him out of the volcano and to safety.
The Berbils and the Cats celebrate their newly formed friendship with a feast where the Berbils offer to help build the Cats Lair.
Wilykit and Wilykat are playing in the forest when they discover that the Mutants have enslaved a race of primitive beings whom they refer to as Brute-Men and are forcing them to build Castle Plun-Darr. The Mutants are extremely cruel in their treatment of the Brute-Men and beat them severely if they falter. Before the Thunderkittens can do anything, they are spotted by Monkian who chases them but they manage to give him the slip.
Meanwhile, construction of the Cats Lair is proceeding very well thanks to the efforts of the Berbils. Wilykit and Wilykat arrive at the lair and report the Mutants' actions to the rest of ThunderCats. Ro-Bear-Bill, who is also present there, further informs the Cats that the Brute-Men are gentle beings who lack much intelligence. The ThunderCats, led by Lion-O, set-off to rescue the Brute-Men in the ThunderTank, leaving Kit and Kat to guard the Lair.
The ThunderCats arrive at Castle Plun-Darr and the ThunderTank breaks through the surrounding barricade with ease. Lion-O enters the Castle while the rest of the Cats split up and go round the sides and back of the Mutants' fortress. Cheetara encounters Jackalman, Tygra runs into Monkian and Panthro squares off with Slithe. All three Mutants are easily overpowered by the Cats.
In the mean time, Lion-O manages to locate the Brute-Men's cells and sets them free. Slithe arrives and after witnessing the freed Brute-Men, he decides to turn the situation to his advantage. He throws a canister of Warp Gas in the midst of the Brute-Men and the vapors cause the meek creatures to turn into raving monsters and they start attacking Lion-O. They then turn their attention to Panthro who has just arrived inside the Castle but just as they are about to attack Panthro, the effects of the Warp Gas wear off and the Brute-Men revert to their docile nature. Slithe throws another canister of the gas but Lion-O uses the Sword of Omens' force field to push the gas back towards the Mutants who now end up being on the receiving end of the Brute-Men's rage and quickly retreat inside the castle. The Brute-Men rejoice at being freed and return to their homes.
While out for her morning jog, Cheetara is drugged and captured by the Mutants as part of Mumm-Ra's plan. Mumm-Ra then transforms himself into a Thunderian named Pumm-Ra and when Cheetara regains consciousness, he tells her that he saved her from the Mutants. He also tells her that he too was a resident of Thundera and managed to escape its destruction by fleeing in a small spacecraft.
Cheetara takes Pumm-Ra back to Cats Lair where he tells his story to the rest of the ThunderCats. Lion-O is keen to induct Pumm-Ra into the ThunderCats but Panthro and Tygra are wary and decide to give Pumm-Ra a week's probation. That night, while the ThunderCats sleep, Pumm-Ra sabotages both the Cats Lair and theThunderTank and also succeeds in stealing the Sword of Omens and the Claw Shield.
The next morning, Lion-O and Snarf are left to guard the Lair while the rest of the Cats go off to the Thundrilliumfields. Pumm-Ra seizes this opportunity and signals the Mutants to attack. He himself tries to use the Sword of Omens against Lion-O but because it cannot be used for evil purposes, a bolt of lightning knocks it and the Claw Shield out his hands. The Mutants attack using the ThunderTank but the rest of the Cats arrive in time and drive them off.
Meanwhile Pumm-Ra locks himself inside Cats Lair. Tygra suggests an alternative route into the Lair and he enters the Power Exhaust pipe into the fortress. The rest of the ThunderCats eventually manage to enter the lair and finding himself cornered, Pumm-Ra transforms back to Mumm-Ra and teleports back to his pyramid.
Snarf helps a baby Unicorn escape from being caught by a gang of pirate raiders known as the Berserkers who are led by the ruthlessHammerhand. But Snarf himself ends up being captured by them and being forced to work as a "Beast of Burden" after Hammerhand deems him too "unnatural" to eat.
Meanwhile, Lion-O encounters the mother Unicorn being attacked by a Tree Monster. Lion-O succeeds in rescuing the unicorn, but in the process loses the Sword of Omens to a Giant Crow who swipes it from his hands. To repay him for his help, the unicorn mother gives Lion-O a special ring which teleports Lion-O onto the crow's back and he is able to retrieve the sword. Upon landng back on the ground, the sword warns Lion-O that a fellow ThunderCat is in danger. He uses the sword's "Sight Beyond Sight" vision and sees Snarf's plight. He immediately rushes off to rescue his friend.
As he is making his way towards the beach, Lion-O comes across the Unicorn Keepers and their herd of unicorns. Initially the husband and wife are wary of Lion-O, but he assures them that he means them no harm and uses the sword's "Sight Beyond Sight" to show them that he rescued one of their unicorns from being devoured by the Tree Monster. At that moment, the Berserkers arrive with Snarf as their captive and attack Lion-O. A fierce battle ensues between the Lord of the ThunderCats and Hammerhand but it is cut short when one of the Berserkers threatens to harm Snarf if Lion-O continues the duel. The Berserkers then make off with Snarf and the baby Unicorn in tow.
Lion-O pursues the Berserkers to their ship and while he is battling the pirate raiders, Snarf and the baby Unicorn fall overboard. Lion-O dives in to the ocean after them and summons the other ThunderCats. Panthro and Cheetara come to his aid in the ThunderTank thanks to the tank's new "aquatic mode". Hammerhand fires laser beams from his ship at the Cats but Cheetara retaliates by firing lasers from the tank. Panthro then starts to rapidly circle the Berserkers' ship, creating a strong whirlpool which caused it to sink along with its dastardly crew. Lion-O and Snarf return the baby Unicorn back to its mother before heading back home.
Inside Castle Plun-Darr, the Mutants are extremely dissatisfied with the food that is being served to them by their Lizard Cook. Monkiansuggests that a "woman's touch" is needed in the castle and Slithe, concurring, orders the simian to find a few servants.
Nayda, one of the Warrior Maidens of Third Earth, is fishing when Monkian suddenly abducts her. Nayda cries out for help and in the blink of an eye, her elder sister, Willa, armed with bow and arrows, arrives and foils Monkian's plans, sending him fleeing into the forest. The two sisters are upset at the way their world has changed after the sudden arrival of the two alien groups.
Back at Cats Lair, Lion-O decides to take the ThunderTank for a joyride, inspite of Snarf's objections. Lion-O loses control of the tank and it zooms around erratically with the young lord still inside. Hearing all the commotion, Panthroemerges form the lair, jumps into the tank, and stops it just as it is about to go over a cliff.
Panthro is less than happy about Lion-O's antics and points out that the Thundrillium supply is dangerously low and without it there will be nothing to fuel the tank or the lair. The ThunderCats decide that they should venture out into their new world and search for Thundrillium. Panthro provides each Cat with a Thundrillium Detector which would start to flicker whenever the substance is detected nearby. The ThunderCats each set out in a different direction.
Having overheard the ThunderCats talking about their dwindling fuel supplies, Monkian returns to Castle Plun-Darr and reports this information to his fellow Mutants. Seeing this as an opportunity to defeat their feline nemeses, they set-off to prevent the ThunderCats from succeeding.
While passing through a forest, Lion-O comes across WIlla being attacked by a giant dinosaur like creature known as theLizarthon. Lion-O scares it off using his Claw Shield. He introduces himself to her but she remains suspicious of him.
Meanwhile in his search for Thundrillium, Tygra wanders into a strange cave which is giving a strong reading on his detector. Unbeknownst to him, he has entered the Cave of Time and anyone who ventures in there, ages rapidly until they die. Tygra begins to age at an accelerated rate and upon realizing this he tries to turn back but he has become too weak to walk out of the cave.
Still in the forest, Lion-O is ambushed by the Mutants but this time Willa saves him by firing arrows filled with sleep gas at the Mutants who make a hasty retreat. As Lion-O is thanking WIlla for her help, the Sword of Omens warns him about Tygra. Willa tells him that only someone who is fast enough to avoid the cave's effects can bring Tygra out safely. Lion-O immediately thinks of Cheetara and summons the other ThunderCats.
Panthro, Cheetara, Lion-O and Willa arrive at the Cave of TIme and Cheetara sprints in and brings Tygra out with her in a matter of seconds. Willa tells them of a pool that can heal Tygra called the Geyser of Life. The group decide they need to get Tygra to it as fast as possible. When they arrive, they find that the geyser is guarded by the fierce Wing-ed water snakes. Lion-O and Cheetara distract the flying serpents while Tygra enters the waters and comes out young again.
While Wilykit and Wilykat are out in the woods making a map of the area as per Tygra's instructions, they hear a commotion and go to investigate. The cries for help are coming from an oldWolo Traveller who is being robbed by what appear to be two gargoyles. The Thunderkittens intervene and rescue the Wolo but the gargoyles make off with his bag containing a gold bracelet, a gift for his daughter's wedding to which he was heading. The Wolo informs them that the gargoyles work for Baron Karnor who lives in the nearby Black Tower
Wilykit and Wilykat head for the tower and upon reaching it, find that there is no way into it. Wilykat tries to force open the rusty old lock on the tower's door while Wilykit circles the tower to look for another entrance. When she returns she finds that her brother has disappeared without a trace. She calls out to him but gets no response.
Meanwhile, Lion-O is enjoying a relaxing swim in a small lake near Cats Lair. As he gets out, the Sword of Omens warns him that a ThunderCat is in danger. Using the sword's "Sight beyond sight" vision, Lion-O sees Wilykit desperately searching for her brother. He immediately rushes off to the tower that he saw in the sword.
When Lion-O arrives, Wilykit tells him what has transpired. Lion-O tries to force open the lock just as Wilykat had done. Immediately a trap door opens beneath them and both Lion-O and Kit drop down and find themselves inside the tower. They call out to Wilykat who replies that he is in a cage at the top of the tower.
As Lion-O and Wilykit start to make their way up the tower, they come across a trick staircase which prevents them from climbing it. Lion-O elongates the Sword of Omens and uses it as a pole vault to get him and Wilykit up the stairs. As they continue their ascent, an iron fence suddenly drops down from the top separating Lion-O and Wilykit. They both continue on their separate paths.
Lion-O encounters a giant hungry Octopoid with snapping claws but manages to subdue the beast. He also manages to barely jump across an extending acid-filled pit and bypass blades that shot down from the ceiling. Wilykit on the other hand first contends with having to cross a slim bridge over a raging inferno and then a room filled with laser-shooting statues and finally a hallway packed with swinging blades.
At this point Lion-O and Wilykit have reunited and finally locate Wilykat in a cage, hanging from the roof. They free him and at that point a door opens and they hear a voice telling them to enter. They cautiously enter the room which turns out to be the baron's treasure room. There they find the baron's dead body sitting on the chair. The voice that told them to enter turns out to be a recording and the doors of the treasure room shut by themselves, trapping the three ThunderCats.
While Lion-O, Wilykit and Wilykat are searching for a way out, a panel opens in the roof and a piece of jewelry is dropped into the room. Wilykit recognizes it as the Wolo's wedding bracelet. The ThunderCats make their way out via the roof and emerge at the top of the tower where they find nothing but stone gargoyle statues. The statues suddenly leap to life and attack the Cats. Lion-O summons the other ThunderCats and they arrive shortly in the ThunderTank and help to fight off the gargoyles. The Cats then head back home but not before stopping at the Wolo village to return the bracelet.
Inside Cats Lair, Panthro and Tygra are concerned about the multiple earthquakes which are occuring in the area. Tygra goes out to investigate but the ground underneath his feet opens up and he falls down the crack. As he climbs out, he is attacked by a giant worm. The worm drags Tygra with it into the ground.
Undeground, Tygra notices a trail of glowing slime left by the worm and starts to follow it. He first encounters twoMolemen who are just as clueless about the quakes as he is. As Tygra continues to chase the worm, he meets Silky, a plant with a human face. She welcomes Tygra to the Garden of Delights and offers him a yellow fruit. Tygra tries to resist but eventually ends up taking a bite out of the fruit. He immediately starts hallucinating and enters a sort of euphoric state where he imagines himself flying.
Now that Tygra is addicted to the fruit and completely under its spell, Silky transforms and reveals herself to be Mumm-Ra. The evil mummy gives Tygra another fruit but in exchange he has to steal the Sword of Omens for him.
Back outside Cats Lair, Panthro and Wilykat are using the ThunderTank to clear up the fallen trees that were uprooted by the earthquakes. Tygra returns back to the lair, still in a dazed state and almost gets hit by the tank. Panthro gives Wilykat a chance to drive the tank but he is unable to control it and the vehicle plunges down one of the crevices. Thankfully neither of the two are hurt. Lion-O and Cheetara climb down the crevice as well to investigate the network of tunnels created by the giant worm.
Meanwhile, Tygra, who is unable to sleep due to Silky's voice echoing in his head, steals the Sword of Omens and delivers it to Mumm-Ra in his pyramid. Knowing that the sword cannot be used by evil, Mumm-Ra summons the Mutants and the two concur that they need to find a "pure spirit" for their scheme to succeed. They set a trap which teleports their chosen "pure spirit", Willa, inside Mumm-Ra's pyramid. Mumm-Ra then tries to tempt the Warrior Maiden with unlimited power if she sides with him. However, the sword's "Sight beyond sight" shows Willa what has transpired so far but she plays along and pretends to crave the power to rule Third Earth.
The Warrior Maidens led by Willa attack Panthro and Tygra and tie them up. The Mutants and Mumm-Ra arrive and lock up Lion-O, Cheetara and Panthro in an inescapable room inside Cats Lair. Panthro then resorts to his ingenuity and uses his belt insignia, which is actually a flying recording device. He uses a remote control to guide the device out of the room via the skylight. Outside, the device captures the discussion taking place between Mumm-Ra and Tygra in which, in exchange for another fruit, Tygra reveals that Mumm-Ra will never be fully successful as long as Lion-O lives. Mumm-Ra, realizing that Tygra is right, tells Willa to prepare for battle as he hands the ThunderCat another fruit. Tygra however, only pretends to eat the fruit and Willa is the only one who sees it.
Mumm-Ra, Willa, the Mutants and the captive ThunderCats are all transported to some sort of ancient ruins where Mumm-Ra begins to proceed with his sinister plan. However, he is interrupted by Tygra who is now back to his senses. At that point Willa frees Lion-O and throws him the sword. The ThunderCats all spring to action and once again defeat the Mutants and Mumm-Ra.
While taking a walk through a field of long dried grass, Lion-O andSnarf come across what appears to be a giant blue metal container. Hearing voices coming from within it and thinking that someone inside might need help, Lion-O opens the pod, ignoring Snarf and the prominent "DANGER" warning written on the container.and ends up releasing the three captives inside it who immediately disappear in the grassy field but not before one of them, Quick Pick, steals the Sword of Omens and Snarf's Secret Coin Purse. Lion-O and Snarf try desperately to search for him in the grassy field but in vain.
They are startled by the arrival of Mandora, of the Interplanetary Control Force, on her Electro Charger. She is extremely annoyed and berates Lion-O for releasing three of the galaxy's most wanted evil-doers. She had left them there until they could be transported to the Gray Penal Planet. She then demands that Lion-O and Snarf help her apprehend the escaped prisoners as they are familiar with the surrounding areas. Lion-O agrees as this may be his only way to get the sword back and the three of them zoom of on the space bike.
Meanwhile, one of the escapees, Plutar, has made his way to the Living Ooze. He and the ooze decide to team up to take down the evil chaser. Mandora, Lion-O and Snarf arrive shortly and as Mandora tries to land on the thin riverbank next to the ooze, the anthromorphic slime drags the trio and their vehicle towards itself and they become trapped in the ooze. However, Mandora manages to free herself and fires her "Enzyme catalyzer" at the ooze, immediately dissolving it. Plutar tries to attack her from behind but Mandora zaps him as well. Mandora then takes Plutar back to the cell sled on her Electro Charger while Lion-O and Snarf wait for her to return.
As soon as Mandora leaves, Lion-O hears the roaring of a motor which turns out to be Burnout, the second escapee, charging towards an unsuspecting grazing deer. Lion-O rescues the defenseless animal by rolling a giant boulder in the path of Burnout. The mechanical monster now turns his attention towards Lion-O and charges him. At that moment, Mandora arrives and she and the young lord manage to subdue Burnout. This time it is Lion-O's turn to take the prisoner to the holding cell while Mandora tries to locate Quick-Pick using a tracking device. She activates another tracker on her bike whcih will help Lion-O to locate her.
While hot on Quick-Pick's trail, Mandora gets captured by Mudhogs and taken underground. There she finds Quick-Pick who is also one of their prisoners. When Lion-O arrives, he too is captured and tied by the hogs. He notices that the king of the Mudhogs has the Sword of Omens and Snarf's Coin Purse around his belt. Quick-Pick uses a distraction to steal the sword from the king and throws it towards Lion-O who loses no time in summoning his friends. The ThundereCats arrive shortly in the ThunderTank and Panthro uses the vehicles instense headlights to scare off the Mudhogs.
While fleeing from a fierce thunderstorm, two Bolkins, Hurrick andBundun, seek shelter under a giant tree. Before they even get a chance to catch their breath, a bolt of lightning rips the tree apart, revealing a hidden chamber underneath it. Inside the crypt, the two Bolkins push a giant stone slab, thinking that there might be treasure buried underneath it but instead a ghostly apparition emerges from it. The Bolkins quickly recognize the ghost as being that of the legendary Grune the Destroyer, who ravaged Third Earth centries ago. Hurrick and Bundun flee for their life as Grune makes his way out of the tomb.
Looking for Thundrillium to replenish his strength, Grune stumbles upon Cats Lair. Inside the lair, the ThunderCats start witnessing paranormal activities such as drops in temperature and strange noises. A piece of the lairs' wall rips away and pins Panthro against a wall. The lair's Thundrillium supply then starts draining at an accelerated rate. Tygra tries to stop the outflow but is unable to. Suddenly, Grune's ghost materializes in front of the ThunderCats, taunting them. The Cats try to fight him but it is in vain as Lion-O describes it as "fighting air". Grune then grows to an enormous size and before disappearing, he promises the Cats that they will meet again very soon.
The next day, Grune terrorizes the various peaceful inhabitants of Third Earth such as Wolos, Bolkins and Berbils by flattening their villages. The Third Earthers come to the ThunderCats, asking to be rescued from the menace. They also inform the Cats that Grune was demanding "Fire Rocks". Hurrick and the Wolo Traveller point out that they didn't have any as it had been forbidden to mine them for over a hundred mega-years due to their power being too difficult to control. Tygra recalls that they had a similar element on Thundera known as Thundrainium. Lion-O promises to help the Third-Earthlings even though he is not quite sure how.
Meanwhile, Grune had managed to locate some Thundrainium and forges a Battle Club out of the substance. Back at the Cats Lair, the ThunderCats are assessing the situation, wondering how the ghost knew so much about them. Lion-O tries to use the Sword of Omens' power of Sight Beyond Sight in an attmept to find out more about Grune but sees nothing. Tygra points out that it is because the Eye of Thundera has no psychic powers. Eventually, it is up to Cheetara to use her Sixth Sense and in so doing, she reveals that Grune used to be a ThunderCat who fought alongside Jaga to protect Thundera against all invaders. But greed overcame Grune and he started destroying and looting. Jaga intervened and after a lengthy battle between the two, Grune was banished from Thundera and set adrift in space. Panthro guesses that Grune's spaceship must have somehow found its way to Third Earth and that is how he ended up there.
Suddenly the whole lair starts shaking and when the ThunderCats go out to investigate, they see that a giant Grune is pounding at the lair with his mace. Still not sure how to attack Grune, Lion-O stumbles upon the answer to the mystery."We fight a ghost, with another ghost. The mightiest ThunderCat of all!", he proclaims and uses the sword to call forth the spirit of Jaga. Grune is pleased as that was his plan all along, to draw out Jaga so that he could have a rematch.
The two spirits engage in battle but Grune's Thundrainium mace weakens Jaga and he manages to disarm the ThunderCat patriarch. Lion-O throws his sword to Jaga and the battle resumes but Jaga is still continuing to get weaker due to the effects of the Thundrainium. Seeing this, Lion-O tells Jaga to take his strength. Jaga is reluctant, but Lion-O, as Lord of the ThunderCats, commands it. Armed with Lion-O's strength, Jaga defeats his opponent with ease. Grune, then pretending to offer his hand in friendship, grabs the Sword of Omens from Jaga. However, the sword pulls Grune up into the sky and disintegrates him. Jaga returns the sword and Lion-O's strength back to the young lord.The next day, Hurrick and Budun come to the Cats Lair and reveal that they were the ones responsible for freeing Grune and that they were sorry. Panthro is angry at them but Lion-O tells him to take it easy and points out that even though the Bolkins made a mistake, mistakes can be valuable if one learns from them.
Mumm-Ra asks Nemesis to show him a way to defeat the ThunderCats so that he can rule Third Earth. The force of darkness tells him to free princess Ta-She, from her Time Warp prison and use her power of the Doomgaze to defeat the ThunderCats. Mumm-Ra summons Ta-She in her prison and she agrees to share the power of the Doomgaze with him if he can free her from the Time Warp prison. Initially, Ta-She believes that her freedom is impossible since only she knows the "key" to the Time Warp prison. Mumm-Ra however, reveals that he too knows the key to free her which consists of a tuft of a cheetah's hair, a Berbil's tear, a shoe from an enchanted unicorn and a hero to take her place in the Time Warp prison.
Outside Cats Lair, Lion-O is getting training lessons from Panthro when the young lord gets distracted by a dark cloud in the sky which is moving in the opposite direction to all the other clouds. He calls upon the Sword of Omens' "Sight beyond sight" vision which reveals that the cloud is actually some kind of air-borne jellyfish and that it is headed straight for the Berbil Village.
The ThunderCats rush to the village but the Man-o-War Cloud reaches there first and abducts Ro-Bear-Belle. Cheetarazooms after the jellyfish, leaving scratch marks on trees for Lion-O to follow. As she is running, Cheetara gets ensnared in a net by Slithe who chops off a tuft of her hair. Cheetara manages to rip apart the net but before she can do anything, the Man-o-War cloud grabs Slithe in its other tentacle and flies away.
Further along the trail, Jackalman pries off a shoe from a unicorn that he has captured. Lion-O and Snarf arrive but Jackalman flees with the shoe before they can do anything. Lion-O suspects that only Mumm-Ra can be behind all these strange events. He once again uses "Sight beyond sight" and sees a vision of Mumm-Ra and the Mutants, gathered atopMount Anguish. Intending to hit the enemies from both sides, Lion-O tells Cheetara to reach the mountain via thePhosphorus Desert while he and Snarf scale the Crumbling Cliffs of Vertigo.
They reach Mount Anguish where a ceremony is in progress and Mumm-Ra has begun his incantation. He then summons Ta-She who floats down from her boat. Lion-O is mesmerized by her beauty and fails to act when Mumm-Ra forcefully draws out a tear from Ro-Bear Belle. Lion-O finally springs into action at which point Mumm-Ra reveals that the young lord was the hero who would take Ta-She's place in the Time Warp prison. Lion-O manages to summon the other ThunderCats using the Sword of Omens before Ta-She immobilizes him using the Doomgaze. Panthro, Tygra, Wilykitand Wilykat jump into the ThunderTank and head to Mount Anguish but the tank gets stuck in the Field of Daggers.
Ta-She then tries to use the Doomgaze on Cheetara but being a woman, she is immune to Ta-She's control and she removes the cloak that Ta-She had put on Lion-O and throws it at Ta-She who is pulled back into her eternal prison. At that point, the other ThunderCats arrive and a fierce battle ensues between the Cats and Mumm-Ra. Sensing that he has used up too much of his power, Mumm-Ra retreats back to his pyramid.
Inside Cats Lair, Panthro is tracking a giant meteor which has just entered Third Earth's atmosphere. Further analysis of it shows that it is composed entirely of pure Thundrillium and Panthro deducs that it must have been a part of Thundera. The ThunderCats are pleased with this discovery as their fuel supplies are running low. Panthro tries to bring it in but is unable to due to the lair's Thundrillium supplies being on the verge of depletion. He continues to track it on reserve power supply. The meteor flies overhead, scaring several of the inhabitants of Third Earth, like the Warrior Maiden s, the Living Ooze, some unicorns, and the Berbils, before eventually crashing into Hook Mountain.
Lion-O decides to go after the meteor alone. Tygra warns him that the Snowmen of Hook Mountain are savage and proud but Lion-O is undeterred. Cheetara gives him a red cloak to keep him warm and the young lord sets off on his perilous journey. Shortly, he reaches the rugged snowy terrain at the foot of the mountain and unbeknownst to him,Jackalman is spying on him. As he continues onwards, Lion-O senses that someone is following him. It turns out to beSnarf who was worried about Lion-O and decided to secretly tail him. Both of them continue the journey to the top of the mountain.
Meanwhile, Jackalman returnd to Castle Plun-Darr and informs his fellow Mutants that Lion-O is alone on Hook Mountain. Slithe thinks this will be a good opportunity to kidnap Lion-O and force the other Thundercats to do their bidding while they hold him hostage. When Monkian asks how they will reach Hook Mountain, Slithe responds thatVultureman would take them in his Flying Machine. Jackalman, unsure about the safety of the contraption, decides to not join them. So Slithe, Monkian and Vultureman take off in the Flying Machine.
Back at Cats Lair, the Thundrillium supplies have completely depleted and the fortress is left in darkness. Panthro initially proposes that they just sit and wait until Lion-O signals them with the Eye of Thundera. Cheetara, however, sensing that Lion-O could be in danger, feels that they should go after him. Panthro agrees and the ThunderCats set off for Hook Mountain in the ThunderTank.
Lion-O is still continuing his ascent up Hook Mountain and uses his Claw line to climb some of the more perilous cliffs. He and Snarf finally reach the summit where they see the Castle of the Snowmen. The drawbridge of the castle opens and Snowman emerges, armed with a lance and shield and riding Snowmeow. When Lion-O tells the Snowman that he has come for the meteor, the Snowman refuses to give it to him and challenges him to a duel. The two engage in battle and the Snowman knocks the Claw Shield out of Lion-O's hand. Then the spirit of Jaga appears and reminds Lion-O that Snowmeow is a cat and Lion-O, being lord of the ThunderCats, has power over all cats. At that instant, Snowman charges but Lion-O commands Snowmeow to halt which the big cat does. Snowmeow's sudden stop throws Snowman of the cat's back and into the Bottomless Chasm where he lands on a legde.
Using his Claw line and the sword as an anchor, Lion-O climbs down the chasm to rescue the injured Snowman. Suddenly, the Mutants arrive in the Flying Machine and try to pull out the sword ut Snowmeow foils their plan by clawing and jumping on the wings of the mutant aircraft. Lion-O emerges from the chasm, carrying Snowman on his back. Slithe orders Vultureman to attack Lion-O who retaliates by using the Sword of Omens to call the other ThunderCats. Seconds later, the ThunderTank arrives at the scene, firing its lasers at the Mutants who make a hasty retreat.
Snowman tells Lion-O that the young lord proved that he values honor, courage, and friendship, and so he has earned the meteor as well as the Snowman's friendship. Lion-O tells him that if he evers need help, the Snowman can call on the ThunderCats. The Cats bid farewell to Snowman and snowmeow and head back home in the tank.
The Mutants set a trap for the ThunderCats by first ambushing and stealing from a Tabbut. The cries of help from the Tabbut attractCheetara and Tygra, just as the Mutants anticipated. As soon as the ThunderCats arrive at the scene, Monkian drops a sticky net on them and traps them. Inside the Cats Lair, the Sword of Omens warns Lion-O and he and Panthro set out in the ThunderTank to rescue their fellow Cats. Panthro maneuvers the tank's jaws to free Cheetara and Tygra from the net. The ThunderCats then turn their attention to the Mutants who quickly flee from the scene.
Inside Castle Plun-Darr, the Mutants are upset that they get constantly defeated by the ThunderCats. They concur that the reason for this is that while the ThunderCats were able to salvage most of their technology, the Mutants' technology lies buried beneath the Desert of Sinking Sands thanks to Mumm-Ra. They go to the Black Pyramid and eventually manage to convince Mumm-Ra to raise their spaceship. From the raised Mutant Mothership, the Mutants gather their equipment as well as SkyCutters and a NoseDiver and transport it all to Castle Plun-Darr.
Armed with new vehicles, the Mutants launch an attack on Cats Lair with Jackalman and Monkian piloting SkyCutters and Slithe driving the NoseDiver. Panthro and Lion-O decide to face the NoseDiver in the ThunderTank, while the rest of the ThunderCats try to attack the SkyCutters using the lair's Laser Beams. Slithe tricks Panthro into following him over a cliff and into the ocean. The NoseDiver, being amphibious, is able to easily navigate through the water but the ThunderTank sinks and gets wedged in an undersea canyon. Using diving equipment from under their seats, Lion-O and Panthro swim out of the tank and try to push the vehicle but Slithe returns on the NoseDiver and starts firing at them. Panthro then sets a trap for Slithe using a nearby cave which is the den of a Giant Eel. As Slithe tries to avoid the eel, the ends up damaging the NoseDiver's energy module causing it to stall.
Panthro and Lion-O swim onto the shore but are immediately greeted by a barrage of fire from the SkyCutters. Lion-O calls the other ThunderCats and he and Panthro head back into the sea to try and free the ThunderTank. Tygra, Cheetara and the Thunderkittens arrive swiftly and dispatch Monkian and Jackalman with ease. Back underwater, Panthro and Lion-O are attacked by a pair of Sea-Quines. Panthro is surprised at the unexpected aggressive behaviour of these normally gently creatures. Lion-O then spots the reason, a baby Sea Quine who is trapped underneath the tank. Panthro and Lion-O try frantically to budge the tank but remain unsuccessful even with the help of the adult Sea Quines. Just then, Slithe returns on the NoseDiver to attack the Cats once again. Lion-O fires a harpoon from the tank and it attaches itself to the NoseDiver which ends up pulling the tank free and releasing the baby Sea Quine. With the NoseDiver damaged, Slithe retreats while Panthro and Lion-O drive the tank onto the shore to meet up with the rest of the ThunderCats.
While Wilykit and Wilykat are trying out their new Spaceboards andPanthro is fitting voice-activated communicators in all the ThunderCats' weapons, Lion-O is sitting atop Mount Anguish, reminiscing about his home planet, Thundera. Seeing Lion-O homesick, Jaga appears and tells him about the Time Capsule, which houses a nuclear opto-crystal containing the entire history of Thundera. Jaga tells him to find this Time Capsule which was lost when their spaceship crashed on Third Earth. Lion-O informs the other ThunderCats about it and they all set off in different directions to find the device except the Thunderkittens, who are told to stay in Cats Lair. However, as soon as the adult ThunderCats leave, Wilykit and Wilykat sneak out on their spaceboards.
Tygra has wandered into some underground tunnels where he encounters the Molemen, burrowing relentlessy. Suddenly the Molemaster appears and is greatly displeased at Tygra's presence in his mines. He attacks Tygra with his whip but the ThunderCat manages to scare off the tyrant using his invisibility as well as fire from his Bolo whip.
Meanwhile, Lion-O's attempt to cross the River of Despair thwarted due to the Black Widow Shark patrolling the river. The Female Unicorn Keeper assists Lion-O by creating a Bridge of Light across the river. As Lion-O and Snarf make their way across the bridge, the shark leaps up repeatedly slamming its body against the bridge. Lion-O tries to use the Sword of Omens to attack the shark but it instead ends up causing the bridge to shatter. Lion-O and Snarf barely make it across as the bridge crumbles completely.
In a swampy area of Third Earth, Cheetara encounters a giant Sea Serpent. The beast lunges at Cheetara but she proves to be too fast for it and tricks it into biting its own tail. Panthro, who is exploring near a shore, comes face to face with a Crabman who snaps off Panthro's Nunchucks with its powerful claw. Panthro manages to get into theThunderTank and escapes the Crabman. Meanwhile, Wilykit and Wilykat, while unknowingly flying over the River of Despair, are attacked by the Black Widow Shark who chews Wilykit's board to bits. She however, is rescued by her brother and the two flee the scene riding on one board.
As Lion-O and Snarf continue their search, the young lord notices something shiny in a far away cave. He uses "Sight beyond sight" and sees that it is indeed the Time Capsule. He uses the sword to call the other ThunderCats. As he enters the cave, Lion-O wonders how the Time Capsule got there as it is quite far away from where they crashed. His question is answered when a huge Caveman emerges from within the cave and claims the capsule as his. While the primitve man is incapable of speech, he uses gestures to challenge Lion-O to an arm-wrestling match and the winner will claim the Time Capsule as his. Lion-O accepts the challenge and the two lock arms. The other ThunderCats arrive and witness the intense match. Lion-O finally manages to win the arm-wrestling match and the Caveman concedes defeat and disappears back into his cave. The ThunderCats take the Time Capsule back with them to the Cats Lair.
Tygra is investigating a raging forest fire near the Treetop Kingdom. He encounters ,Willa who is devastated at the destruction of her home. She explains that since dawn, the Warrior Maidens' territory was being bombarded with giant fireballs. Suddenly Monkian appears on a SkyCutter and tries to attack the two but Tygra pulls the Mutant out of his vehicle using his Bolo whip. Tygra suspects that the Mutants are somehow behind all this and he and Willa head for Castle Plun-Darr.
Back at Cats Lair, Lion-O is feeling restless as he senses that something is wrong. When he asks for Tygra, Panthro tells him that Tygra went out on a scouting mission. Lion-O is concerned about Tygra and feels that he shouldn't have gone alone.
Meanwhile, Tygra and Willa have arrived at Castle Plun-Darr and in order to sneak in, Tygra turns himself invisible and enters the moat surrounding the fortress, hoping to enter it via the underwater intake pipe. Unbeknownst to Tygra, the Mutants had infused Phosphor-R into the moat's water which allowed them to spot the invisile Tygra on their control room screen. Slithe enters the moat driving the NoseDiver and attacks Tygra with the spinning blades on the nose of the vehicle. Tygra manages to avoid Slithe and throws a rock at the NoseDiver which jams up its grinding apparatus. Tygra continues to swim and enters the intake pipe but ends up losing his whip and becomes visible. The pipe turns out to be a trap and steel bars close the end of it, caging Tygra.
Inside Castle Plun-Darr, the Mutants take Tygra and tie him up to the "Four Winds" , a device which is capable of pulling apart all four of its victims limbs. Slithe sets it up in such a way that thecatapults would be activated as soon as the first rays of the sun hit a solar mirror attached to it. The Mutants then leave Tygra and head back ot the control room.
At Cats Lair, Lion-O is unable to sleep and still worried about Tygra. Suddenly the Eye of Thundera wanrs him of danger and upon using the Sword of Omens' "Sight beyond sight", Lion-O sees Tygra' plight and immediately rushes to his aid. He leaps out of the window and repels himself down the walls of the lair using the extanding chain from his Claw Shield. In his haste, he forgets the Claw Shield which is still anchored to the window sill.
Lion-O arrives at Castle Plun-Darr and is greeted by Willa who tells him all that had transpired and hands him Tygra's whip which she found floating in the moat. Lion-O decides to climb the castle walls but realizes that he has forgotten his Claw Shield. Luckily, Willa has an alternative solution. She pulls out a Giant Treetop Spider named"Bushy", who quickly scampers up the castle walls and pulls up Lion-O and Willa with its web lines.
Once Inside the castle, Lion-O and Willa rescue Tygra and the three of them charge through a horde of Reptilian and Jackalmen guards and lock themselves in the room housing the fireball launcher. Slithe and Monkian arrive with more guards and start melting the door of the launch room using a flamethrower.
Seeing their predicament, Lion-O calls his friends using the sword. The other ThunderCats arrive shortly in theThunderTank and Panthro fires a harpoon with pulleys into the launcher room. Willa, Lion-O and Tygra slide down using the pulleys just as Monkian succeeds in melting the door down. However, the fire from Monkain's flamethrower ignites the fuel in the launch room causing a huge explosion, destroying the fireball launcher as well as much of Castle Plun-Darr
Inside Cats Lair, Panthro and Tygra are working on extracting pureThundrillium from the meteor that Lion-O retrieved from Hook Mountain. One of the main impurities that had contaminated the meteor was Gold, which Panthro describes as being "junk" due to its inert chemical nature. He then gathers all the gold and dumps it into the Bottomless Chasm using theThunderTank.
Meanwhile, Lion-O and Snarf are out on another exploring trip and come across a series of small and big caves which are the homes of the Trolls and Giants. Suddenly, a troll appears, riding a giant grasshopper. He introduces himself asGrygory Grygion and goes on to explain that he must ride through the Midnight Woods carrying valuable goods and is afraid that the "Shadow Robber" who lives there will harm him. Lion-O agrees to accompany him on his trip in order to protect him.
The trio soon reach the Midnight Woods where visibility is very poor due to it being dark. A shadowy figure suddenly lunges at Lion-O and attacks the young lord with a whip-like weapon which causes the Sword of Omens to break into two. The intense sparks emanating from the broken pieces of the sword illuminate the scene just enough to reveal that the Shadow Robber is none other than Tygra. At that moment, the troll transfoms into Mumm-Ra and flies away, laughing maniacally.
Lion-O and Tygra realize that they had both been tricked by Mumm-Ra. The young lord commands the sword to show its power but it does not respond. Jaga then appears and informs them that by attacking a fellow ThunderCat, Lion-O had incurred the Curse of Balthaz. Jaga also informs them that the only way to repair the sword was to forge its blade in Star Fire. A nearby volcano was the only source of this fire as a Dwarf Star had once fallen into its core. But since no living being can withstand that heat, Jaga concludes that the sword's powers are thus forever lost.
Unable to accept this horrifying reality, Lion-O runs off towards the volcano and starts climbing it. Tygra and Snarf try to stop him but seeing that Lion-O had completely lost his senses, they hurry back to the Cats Lair to get more help and return shortly with Panthro, Cheetara and Ro-Bear-Bill in the ThunderTank. Ro-Bear Bill leads them to the Enflamer who is the only one who can withstand the volcano's heat and re-forge the sword. However, the Mutants had attacked the Enflamer earlier, draining him of all his fire and only gold can restore his powers.
Panthro and Cheetara head back to the Cats Lair and return with the gold that Cheetara had saved. They dump all the gold into a pit and melt it. The Enflamer crawls into it and disappears. Panthro remembers that he had given Lion-O a locator device to wear and using its signal, he and the rest of the team burrow into the volcano in the ThunderTank and retrieve Lion-O just before he fell into the core.
The Enflamer emergs from the molten gold with his strength fully replenished and flies into the volcano. He then emerges from the crater of the volcano, holding the Sword of Omens which he had re-forged. But he turns against the ThunderCats and starts hurling fireballs at them. Lion-O calls the sword to him and it breaks free of the Enlfamer's hand and returns to its rightful owner. Enraged, the Enflamer starts to blow up the volcano but the ThunderCats manage to outrun the sea of molten lava in the ThunderTank.
Inside the Black Pyramid, Mumm-Ra summons the Driller and instructs him to kidnap Panthro and bring him to his pyramid in exchange for diamonds. Leaving the pyramid, the Driller burrows underground into the Cats Lair. He surfaces inside Panthro's room where the ThunderCat is sleeping. Panthro awakes and the two engage in a short struggle before the Driller drugs Panthro using "Sands of Sleep" causing him to lose consciousness and then drags him underground with him.
The Driller delivers Panthro to Mumm-Ra, collects the remaining half of his diamonds, and leaves the pyramid. Mumm-Ra sets the unconscious Panthro on his Cloning machine and activates it to create a mold of the ThunderCat. He then levitates Panthro and fills the empty mold with a gas which solidifies into an exact replica of Panthro. Mumm-Ra summons the spirit of Hammerhand from the depth of the seas to inhabit his clone body and bring it to life. The evil mummy instructs his creation to terrorize the inhabitants of Third Earth and the clone sets off to bring this task to fruition.
Mumm-Ra transforms into his ever-living form and flies out of his pyramid, carrying the real Panthro with him. Panthro regains consciousness just before Mumm-Ra drops him into the Bottomless Chasm. Luckily, Panthro lands on a ledge deep within the chasm. He starts to climb out of the abyss using his shoulder spikes but is careful to avoid the high intensity Cosmic rays that the chasm emits every thirty seconds.
Back at a Cats Lair, the Sword of Omens warns Lion-O that Panthro is in danger and its "Sight beyond sight" shows him being carried by Mumm-Ra but before Lion-O can see the location, the vision is disrupted by the Cosmic radiation. At that moment, the control room's screen shows the Berbils' fruit fields on fire. Lion-O dispatches Tygra and Cheetara to help the Berbils and he sets off to find Panthro in the ThunderTank. Lion-O eventually arrives at the Bottomless Chasm just as Panthro barely manages to climb out of it. As Lion-O is helping the exhausted Panthro into the tank, he receives a message from Cheetara that the Wolos were being attacked and Lion-O heads for the Wolo Village.
As he arrives at the village, the Wolo Traveller is shocked to see Panthro and claims that the ThuderCat was the one responsible for all the destruction. Lion-O suspects that perhaps Panthro had done so under the influence of the drug that the Driller gave him. But Panthro is adamant that he is innocent. Lion-O tells Panthro to take the tank to the lair while he sorted out the matter.
A short while later, the Wolo runs up to Lion-O and informs him that Panthro had returned and was destroying their village. Lion-O quickly reaches the scene and is shocked to see Panthro wreaking havoc. Thinking that his friend may be under some sort of evil influence, he calls the other ThunderCats, hoping that all of them together may be able to subdue Panthro without hurting him.
Suddenly the real Panthro arrives in the ThunderTank and the two engage in combat. Lion-O wants to help but is unable to tell the real Panthro from the fake. Snarf then suggests that he use the sword as it would only harm the fake Panthro. Lion-O does so and the sword badly burns the clone and he flees from the scene.
The clone Panthro arrives at Mumm-Ra's pyramid, furious that Mumm-Ra did not give him enough power to fight the ThunderCats. Mumm-Ra blames the clone for the failure and tells him that he has no use for him anymore. Mumm-Ra says that with his mold, he can make as many clones as he wishes. The enraged clone lifts the mold and smashes it. He then reverts to his true form of Hammerhand and leaves.
Inside the Black Pyramid, Mumm-Ra's cauldron is showing him a vision of Mongor, a creature who grows stronger by feeding on fear. The image shows the goat demon creating raging fires with his Scythe. Mumm-Ra, who has been searching for Mongor's prison for centuries albeit unsuccessfully, is certain that once released, Mongor will succeed in defeating the ThunderCats.
At Cats Lair, Tygra and Cheetara are puzzled by sudden mysterious earthquakes and a strange force field which blocks their scanners. Out in the ThunderTank, Lion-O, Panthro and Snarf are experiencing the same technical problems with their equipment. They head back to the lair by which time the disturbances had stopped. Panthro declares everything to be normal but Tygra points out that each time the phenomenon occurs, it gets stronger.
At that point, Wilykit and Wilykat admit that they are somehow responsible for all these strange disturbances. They go on to explain that earlier that day, they came across an ancient ruined temple and decided to explore it further. Inside, they found a hexagonal stone slab with strange symbols carved on it. Thinking that there might be a tomb hidden underneath it, they prised the slab and ended up releasing a fearsome goat-like creature.
The adult ThunderCats are extremely annoyed at the ThunderKittens and start berating them for their irresposible and reckless behaviour. Snarf intervenes and tries to explain that the ThunderKittens are only kids and yelling at them isn't the right way to handle the situation. As all the adult ThunderCats are listening to Snarf, Wilykit and Wilykat sneak out of the lair in their spaceboards. Noticing that they are gone and concerned for their safety, the ThunderCats decide to split up and go searching for them.
As Tygra is passing through a forest, he encounters Mongor. The two battle but Mongor ties Tygra up using his own Bolo whip. Next Mongor seeks out Cheetara and ensnares her in a net. Finally, Mongor cofronts Panthro and succeeds in using his own shoulder spikes to bind him and anchor him to the ground. Meanwhile, Wilykit and Wilykat return to the ruined temple and figure out that the secret to defeating Mongor is not to look at him directly.
Having defeated all the other ThunderCats, Mongor seeks out Lion-O and the two engage in combat. Suddenly, Wilykit and Wilykat arrive riding their spaceboards and tell Lion-O not to look at Mongor directly. The ThunderKittens distract Mongor by blowing bubbles at him and Lion-O uses that opportunity to attack the goat demon. He turns his back to Mongor and using his Claw Shield as a mirror, fires a blast from his sword which shrinks Mongor down in size. Finally defeated, Mongor returns back to his tombs and Panthro seals it with a blow torch.
Deep inside Castle Plun-Darr, the Mutants are showing off their latest creation, a Plun-Darrian Warbot to Mumm-Ra. Slithe demonstrates the robot's abilities by making it turn a nearby Frogdog into statue. Even though Mumm-Ra is not impressed by it, Slithe assures him that the robot has a lot more deadly weapons in its arsenal. He then instructs the robot to head to Cats Lair.
Meanwhile at Cats Lair, the ThunderCats are inspecting the Time capsule that they had recovered from the Caveman. The device projects a hologram of Thundera and Lion-O marvels at the beauty of the image. Later that night, Lion-O, who is on watch, decides to try out the Time Capsule himself. When he switches it on, he is standing right in the path of the projector and, as a result he somehow gets transported back in time and space to Thundera, just before the planet's destruction.
The approaching Warbot is detected by the Cats Lair's scanners and the ThunderCats all gather in the control room, alarmed at the sight of the approaching behemoth and at the same time wondering where Lion-O is. Panthro fires lasers at the Warbot but it sends the rays back causing the lair's eyes to shatter. Panthro then employs the Ballista to shoot a variety of deterrents at the robot including fire, ice, a missile and a giant chain but the Warbot manages to overcome all of them.
Back on Thundera, Lion-O meets his old pet, Kano, a saber-tooth cat who leads him to his father, Claudus. There he sees Slithe and Vultureman trying to force Claudus to give them the plans of the Warbot. Lion-O jumps in and sends theMutants fleeing. Claudus then gives Lion-O the plans of the Warbot, hoping that they might prove useful to him in another world, another time. Lion-O tries to convince Claudus to leave with him but he refuses because he has to stay and boost the guidance system on Jaga's ship. As the planet's earthquakes get worse, Lion-O bids his father farewell and leaves.
In the meantime, the Warbot fires huge chains which attach themselves to the Cats Lair's head and pulls out the entire head of the fortress. The robot then jumps onto the lair and fires a grey substance at the ThunderCats which turns them all into statues. At that instant, Lion-O arrives back at the lair and uses the Sword of Omens to free his fellow ThunderCats. He then turns the sword on the robot and pushes it away from the lair. Lion-O shoots out of the lair using the Ballista and lands near the Warbot's feet. As the robot raises its giant foot to crush Lion-O, the young lord inserts his sword into a small red disc on the Warbot's foot. This causes the robot's foot to explode and the entire robot gets destroyed.
While swimming in the ocean, Wilykit gets swallowed by a giant green robotic frog. The robot then starts pursuing the horrified Wilykat who was also swimming with her. Wilykat manages to outrun the metal behemoth by riding a Unicornand runs back to the Cats Lair to fetch Lion-O. When the two arrive back at the scene they discover that Wilykit is safe and that the robot, called Hercules, is controlled by the friendly Dr. Dometone, who actually has come to ask the ThunderCats for help.
At Cats Lair, Dr. Dometone explains to the ThunderCats that he is the director and principal guardian of the Great Oceanic Plug, a device created to seal a giant fissure in the ocean floor and prevent all the water from draining into the earth's core. But recently, the plug had been under attack from the alien Scrape, who wants to drain the oceans to obtain a mineral found on the ocean floors. This resident of planet Blue Plunder pilots a giant electric eel shaped robot and has already succeeded in destroying Samson, one of the two giant robots guarding the plug. The ThunderCats agree to help and Lion-O and the Thunderkittens ride with Dr. Dometone in "Herky" to the plug while the rest of the Cats stay behind to work on an emergency rig.
Inside the Great Oceanic Plug, the crew are out of food and supplies and out of desperation one of them decides to go out for help in a small propulsion sub. However, Scrape's Giant Eel who was hidden nearby, lunges at the sub and devours it whole. Scrape then pilots the eel straight into the plug via the observation deck.
Herky arrives and its occupants see the Giant Eel sticking half way out of the dome of the plug. Lion-O and Wilykat don Shark suits and swim out with a grounding cable which would neutralize the Giant Eel's electric charge. Scrape, meanwhile, notices Herky and drives his Giant Eel straight towards it. The eel wraps itself around Herky and is about to deliver its lethal charge when Lion-O swims up behind the eel and throws the grounding cable on it.
With the eel put out of commission, Scrape jumps into the propulsion sub that he had swallowed earlier and drives out of the eel. Wilykat tries to stop the sub but Scrape captures him. Seeing this, Lion-O calls the other ThunderCats. Meanwhile, Scrape has infiltrated the dome of the Great Ocean Plug and opens the plug. However, Panthro, who has arrived in the ThunderTank with Tygra and Cheetara, encloses the dome in a compressed air bubble to prevent Scrape from succeeding. Tygra then activates the vacuum suction and Scrape gets sucked out of the dome and into the ThunderTank.
Lion-O is alarmed by the Sword of Omens' warning and using "Sight beyond sight" he sees that Jaga has been imprisoned in the Astral World by Nemex, a three eyed, four armed creature, who plans on keeping Jaga there for all eternity. Lion-O quickly informs the other ThunderCats about this and they reach the conclusion that only the Nether Witch might be able to help them. Mumm-Ra, who had been watching the ThunderCats from his cauldron is very pleased as he and the Nether Witch are one and the same. He then transforms into the Nether Witch.
The ThunderCats drive out in the ThunderTank to the Nether Witch. Lion-O insists that he must embark on this mission alone so the rest of the ThunderCats drop him off at the Bridge of Slime and leave. As he crosses the bridge, the Gaw Rak Rak, a two headed monster, emerges from the water and lunges at him but Lion-O manages to subdue it and crosses the bridge to reach the Pit of the Nether Witch.
Meanwhile inside Castle Plun-Darr, Mumm-Ra has informed the Mutants about Lion-O's absence and that they must use this opportunity to their advantage. Vultureman prepares a "Thundrainium Cannon" and the Mutants set out in their vehicles to attack Cats Lair.
Back inside the Pit of the Nether Witch, Lion-O encounters a number of strange apparitions and creatures before finally coming face to face with the Nether Witch herself. Lion-O asks her to transport him to the Astral World but she warns him that once he is there, he can never return back to Third Earth. Willing to do anything to save Jaga, Lion-O agrees and the sorceress starts her incantation. As Lion-O starts de-materializing, Mumm-Ra reveals his true self and the young lord realizes that he has been tricked just before he disappears completely.
Lion-O materializes in the Astral World, near the fortress where Jaga is being held prisoner. Using the line from his Claw Shield, Lion-O begins ascending the steep walls of the tower. Suddenly, he is attacked by the Astral Moat Monster which jumps up at him from the moat surrounding the tower. The creature then starts pursuing Lion-O by using its sharp claws to to climb the wall. Lion-O zaps it with a beam from the Sword of Omens and the creature falls back into the water, never to be seen again.
Once inside Jaga's prison cell, Lion-O is confronted by Jaga's captor, Nemex who shoots energy beams at the young lord. Lion-O counteracts his beams with the Sword of Omes and knocks down Nemex. Lion-O then quickly frees Jaga and as the two are running through the prison, they hear calls of help from a nearby cell. They break into it to find, Brodo, an old man who was once a powerful magician on Third Earth but was tricked by Mumm-Ra and imprisoned in the Astral World. Lion-O and Jaga take Brodo with them as they escape the prison fortress.
Outside the prison, the Sword of Omens shows Lion-O that Cats Lair is being attacked by the Mutants and the Thundrainium shells that they are using in their cannon is weakening the ThunderCats, making them unable to fight back. Lion-O feels helpless as he cannot help his friends when they need him the most. At that point, Brodo reveals that he will use his powers of good to transport Lion-O to to his own world and he begins his incantation.
Lion-O materializes back outside Cats Lair and using his sword, destroys the Thundrainium Cannon. The arrival of their lord gives the rest of the ThunderCats renewed strength and they are able to defeat the Mutants
Lion-O has to brave an ice palace to rescue an endangered bird from the clutches of a cruel and greedy queen.
While driving through the forest in the ThunderTank one night, Lion-O and Panthro see a glowing object streaking through the night sky. They try to keep pace with it but the tank stop abruptly. Upon inspection, Panthro finds that the Thundrillium module on the tank ran down, even though Snarf was supposed to recharge it. Panthro heads off to the Cats Lair to fetch a spare module, leaving Lion-O to guard the tank.
Panthro reaches Cats Lair shortly, where Snarf is serving dinner to the rest of the ThunderCats, and asks him about the spare module. Snarf can't find it at first but eventually remembers where he kept it. As Panthro is leaving, Snarf asks to join him but Panthro refuses, saying that there is no need as he will return with Lion-O very soon. However, Snarf gets a bad feeling that Lion-O is in danger and sneaks out after Panthro.
Meanwhile, Lion-O hears strange music coming from the nearby Berbil Village and heads off to investigate. Upon reaching, he sees the source of the music is a beautiful bird, who Ro-Bear-Bill tells him is the rare Arrietta Bird. The birds singing ripens the Berbils' fruits and ensures that they will get a good harvest.
Suddenly, the streaking object that Lion-O had seen earlier returns and it turns out to be a rocket powered sleigh. Ro-Bear Bill explains to Lion-O that the occupant of the strange flying vehicle is Queen Tartara of the Crystal Kingdom and she is always trying to steal the Arietta Bird so that it may sing for her alone. As the vehicle makes a second pass, one of the drivers manages to nab the bird. Lion-O springs into action and grabs onto one of the runners of the sleigh as it flies off to the Crystal Kingdom.
When Panthro arrives back at the tank and does not see Lion-O, he goes to the Berbil Village where Ro-Bear Bill explains all that had happened. Panthro then gets in the tank and drives off towards the Crystal Kingdom but is unaware that Snarf had stowed away in the tank. Half way up the mountain, Panthro comes to a fork in the road and as he gets out of the tank to investigate, he hears Snarf and discovers the stowaway. He then tells Snarf to wait there as he checks out the two paths. Snarf however, notices Lion-O's footprints in the snow and races off following the trail.
Lion-O who had fallen from the flying sleigh near the Crystal Kingdom, sneaks into the palace by disguising himself as one of the guards. He makes his way into Queen Tartara's treasure room where the Arietta Bird is being held but before he can do anything, he is discovered by the queen who encases him in a giant crystal.
Snarf follows Lion-O's footprints all the way to the Crystal Kingdom and then burrows under its walls. He surfaces in the treasure room and uses the Arietta Bird's high pitched voice to break the crystal encasing Lion-O who immediately summons the ThunderCats. Panthro arrives in the ThunderTank, breaking through the wall of the palace. Lion-O and Snarf hop in the tank and the trio drive out destroying another wall. This causes the entire palace to start collapsing and the Arietta Bird escapes by flying out through a hole in the roof.
A huge spaceship lands in a clearing in the forest and from it emerges Safari Joe, the best big game hunter in the galaxy. After having successfully hunted Big Cats, Aqua Cats and Sky Cats, Safari Joe now has his eyes set on hunting ThunderCats. The only other occupant of the ship is his robotic assistant, Mule, who immediately gets to work unloading supplies as well as setting up camp and the Holojector device which displays the profiles of Safari Joe's preys.
In another part of the forest, Wilykit and Wilykat are cruising on their spaceboards with Wilykit showing off her skills. Safari Joe, who is secretly stalking them from the nearby bushes, fires his gun at their spaceboards, breaking them to pieces. As the ThunderKittens fall to the ground, they are caught in giant bags which Safari Joe had set for them.
At Cats Lair, while Lion-O and Snarf are enjoying a game of "Kick the Bucket", Panthro is worried about the "electronic blind" in the middle of the forest. Unbeknownst to him, the blind has been set up by Safari Joe to conceal his spaceship and his camp. Lion-O tries to use the Sword of Omens' "Sight beyond sight" but even it fails to see past the blind. Tygraand Cheetara decide to check it out on foot.
Back at Safari Joe's camp, the hunter locks up Wilykit and Wilykat in Thundrainium cages and then instructs Mule to start the holojector so that he may see his next prey. The device first displays a hologram of Tygra and then Cheetara and Mule describes each of their strengths and weaknesses. Shortly after, Tygra and Cheetara arrive in the forest and Safari Joe wastes no time in capturing both. He first catches Cheetara using rocket-powered cuffs and then traps Tygra in a water-filled hole. He then locks them up in Thundrainium cages as well before getting the holojector to show him the profile of his next prey, Panthro.
Panthro, who has taken the ThunderTank out to search for his friends, soon locates the electronic blind. Before Panthro can do anything, he is showered by a barrage of explosive shots from Safari Joe which cause the tank to flip over. Panthro attacks using his Nunchucks but Safari Joe fires a round from his gun which materializes into a huge energy bat, the one creature that Panthro fears. The bat terrifies Panthro who becomes so overwhelmed with fear that he is unable to move and the hunter locks him up in a cage as well. Mule then switches on the holojector again to show Safari Joe the profile of Lion-O. As the device displays Lion-O using the Sword of Omens, the holojector shorts out and explodes. Mule explains that the Eye of Thundera defied being analyzed. Safari Joe is amused at the opportunity of having to capture a prey whose strengths and weaknesses he is not fully aware of.
Meanwhile back at Cats Lair, Lion-O is worried about his comrades. At that moment, Jaga appears and informs him about his adversary. He tells Lion-O that Safari Joe is a formidable opponent who knows all of the ThunderCats' weaknesses. Lion-O goes out to rescues his friends but as soon as he steps out of Cats Lair, he is confronted by Safari Joe. The hunter uses every trick in his arsenal on Lion-O but the lord of the ThunderCats manages to defeat each one of them.
Safari Joe then taunts Lion-O to fight him without his sword which Lion agrees to if his friends are released. Safari Joe accepts the deal but as soon as Lion-O throws away his sword, Safari Joe turns back on his word and starts shooting at Lion-O. Deciding to use his wits, Lion-O runs into Cats Lair and dares Safari Joe to come and get him. Inside the lair, Lion-O avoids Safari Joe for a while but eventually slips and falls right at Safari Joe's feet. Before the hunter can shoot Lion-O, Snarf runs up behind him and kicks the bucket right into Safari Joe's back causing him to fall down and drop his gun. Seeing that he is unarmed, Safari Joe, in a cowardly fashion, concedes defeat.
In the end, the ThunderCats take Safari Joe to his spaceship and make him promise never to hunt again and Panthro changes Mule's work directive to make sure that Safari Joe adheres to the promise.
Snarf returns to Cats Lair only to find it deserted. He searches but cannot locate any of the ThunderCats. The only one left in the lair isRo-Bear-Bill who himself does not know what happened to the ThunderCats. Suddenly the Female Unicorn Keeper appears and informs Snarf that the ThunderCats have all been captured, which Snarf finds hard to believe.
She continues to narrate that it all started when the Mutants first started herding her Unicorns, causing them to flee into the Forest of Silence. Her husband came to the ThunderCats for help and they split up and went into the forest to find the unicorns. Lion-O was the first one to be captured. He was shackled by the NoseDiver that the Mutants had purposely left unguarded. Tygra was next to fall victim when he entered and was trapped in a Maze of Light. Next in Line was Panthrowho, similarly to Tygra, was imprisoned inside a giant crystal chamber. The ThunderKittens followed suit whenVultureman used a strong tractor beam from Castle Plun-Darr to catch them. Cheetara was the last one to be caught by the Mutants who used a fake ThunderCats signal to lure her into their trap.
Realizing that he is the only ThunderCat left, Snarf embarks on a mission to rescue his friends. Using his ability to communicate with animals, Snarf calls a giant bat who first flies him to Castle Plun-Darr so that he can find out where the ThunderCats are being held captive. There he overhears the Mutants gloating over their success and learns that his friends are all incarcerated inside Mumm-Ra's Black Pyramid so he rides the bat to that location.
Once he reaches the Black Pyramid, Snarf talks to a spider who enters the pyramid through a crevice and proceeds to tie up Mumm-Ra's sarcophagus using its web with the mummy still inside. Snarf then instructs a woodpecker with a diamond tipped beak to bore a hole in the wall of the pyramid and reaches inside the hole to pull the lever which controls the main doorway.
With the door open, Snarf rushes into the pyramid where he finds all the ThunderCats mummified. He quickly tears the bandages covering Lion-O and hands him the Sword of Omens who uses it to free the other ThunderCats and they all leap into action. By this point, Mumm-Ra who had been struggling to emerge from his web bound sarcophagus, finally manages to open it and transforms into this ever-living form. He then fires energy bolts from his hands at Lion-O who avoids some of them and uses the sword to deflect the others. Mumm-Ra then charges at Lion-O but the young lord uses the sword's blade to show Mumm-Ra his own reflection which causes him to recoil in fear back into his tomb.
While out in the forest with Lion-O, Cheetara suddenly starts receiving transmissions from a distressed alien spaceship which has just entered Third Earth's atmosphere. The signals tap right into her sixth sense and cause her to convulse violently and collapse. Seeing Cheetara's condition, Lion-O immediately summons the other ThunderCats using the Sword of Omens.
The Mutants, who had also been tracking the spaceship's transmissions, see the ThunderCats signal and Slithe sends Monkian to its location to investigate. There he overhears the ThunderCats talking about how the spaceship has formed a link with Cheetara's sixth sense and is controlling her mind as well as draining her strength. Monkian returns to Castle Plun-Darr and informs the Mutants about this. Based on the spaceship's last transmission, Vultureman deduces that it crashed somewhere on Hook Mountain so the Mutants set off for the location.
The ThunderCats take Cheetara back to the Cats Lair as her condition deteriorates further. Wilykit and Wilykat also trace the signal back to Hook Mountain so Lion-O, Tygra and Panthro leave in the ThunderTank, leaving the ThunderKittens and Snarf to take care of Cheetara.
Meanwhile, the Mutants have already located the spaceship but as they approach it, the craft activates its defense mechanism and starts attacking the Mutants. This greatly angers Monkian who retaliates by trying to destroy the spaceship but Vultureman stops him before he does any more damage. The Mutants remove the control unit of the ship and take it back to their fortress. The ThunderCats arrive shortly after and realize that the Mutants have already been there. They take whatever is left of the spaceship back to Cats Lair and from there, Lion-O and the Thunderkittens leave for Castle Plun-Darr while Panthro and Tygra begin repairs on the remainder of the ship.
Inside Castle Plun-Darr, Vultureman is hard at work trying to figure out how the control unit works. Lion-O and the ThunderKittens sneak into the castle and start searching for the control unit. Meanwhile back at Cats Lair, Panthro and Tygra have completed the repairs on the remainder of the spaceship and decide to go to Castle Plun-Darr to help Lion-O. Cheetara insists on going as well despite her condition. They arrive just in time to rescue Lion-O and the Thunderkittens who have been surrounded by the Mutants. Cheetara uses her sixth sense to control the alien spaceship and make it fire blasts at the Mutants who flee from the scene. The ThunderCats then take the control unit back to Cats Lair and attach it to the rest of the ship and it flies off into space.
Inside the Black Pyramid, Mumm-Ra is tired of the Mutants' consistent failures to destroy the ThunderCats. Slithe claims that theSword of Omens is to blame as it keeps on growing stronger each time. Mumm-Ra then summons Hachiman, an ancient samurai warrior and possessor of the mighty sword, the Thunder-Cutter, and convinces him that the ThunderCats are evil. Sworn to the code of Bushido, Hachiman sets out to seek and destroy the leader of the ThunderCats, Lion-O.
At Cats Lair, the ThunderCats are explaining to Nayda how their new "Mutant Attack Warning System" works. Panthrosays that once Lion-O has installed it, the system would help to protect the Warrior Maidens' Treetop Kingdom from intruders. Lion-O and Nayda set off for her home but since the normal route would take them three days to reach, Nayda suggests a shortcut across the "Four Day Drop".
The two soon reach the Four Day Drop and Lion-O begins to cross the long log spanning the abyss. As he reaches mid-way across it, Hachiman starts to cross it from the other end and both meet in the middle. With neither of them willing to back down, they start cutting the log using their swords until one of them concedes defeat. The old log breaks and they both fall down the chasm but Nayda rescues them by firing an arrow with a rope attached to it which they grab and climb up.
Hachiman, still not aware of the identity of Lion-O, says that he is searching for lord Lion-O. The young lord of the ThunderCats reveals that he indeed is the Lion-O that Hachiman is searching for and the two get ready to engage in a duel. However, neither the Thunder-Cutter nor the Sword of Omens agree to draw and both Lion-O and Hachiman realize that the duel is wrong. Hachiman then figures out that he had been tricked by Mumm-Ra and befriends Lion-O. The samurai then cuts down another tree with his sword and it falls across the chasm to replace the one that they broke.
Meanwhile, Slithe and Monkian who had been observing all this from their SkyCutter above, decide to attack the trio. Lion-O, Hachiman and Nayda use the branch of the fallen tree as a catapult and knock the SkyCutter out of the sky. The Mutant craft crashes and Monkian flees, leaving Slithe trapped in the wreck of the SkyCutter. Lion-O decides to take Slithe with them as a hostage.
Monkian reports the events that had transpired to Mumm-Ra who then summons a Ninja to finish the job which Hachiman didn't. The Ninja, in the disguise of Gumla the Tabbut, goes to the Treetop Kingdom to negotiate the release of Slithe on behalf of Mumm-Ra and the Mutants. That night, while secretly carrying out his plan, the Ninja is caught by Hachiman. The Ninja uses Nayda as a hostage, threatening to drop her from her treetop post. At that moment, the Mutants who had been waiting in the nearby bushes, attack the Warrior Maidens. As Lion-O summons the other ThunderCats, the Ninja drops Nayda but Lion-O throws the sword into a nearby tree and she grabs the sword and swings to safety. As Hachiman goes to attack the Ninja, he disappears into thin air. Suddenly the rest of the ThunderCats arrive in the [ThunderTank] and the Mutants run for their lives.
Vultureman builds a state-of-the-art infiltration robot known as the Wolfrat. He presents the robot to Mumm-Ra and assures him that this creation is capable of penetrating the Cats Lair'severy defense. Mumm-Ra, while initially dismissive at Vultureman's new creation, changes his mind after seeing a demonstration of the Wolfrat's abilities. He provides Vulturman with a vial of Miniaturization gas with which to arm the Wolfrat.
The Wolfrat then stealthily makes its way towards the Cats Lair. It avoids detection from both the lair's scan vision as well as the Sword of Omens' sight beyond sight by first transforming into a rock and then a section of the wall. It manages to drill its way into the lair and injects the Miniaturization gas into the ventilation shaft of the lair.
The gas reaches the ThunderCats and shrinks them all down to a mere fraction of their normal height. The Wolfrat takes this opportunity to attack the diminutive Cats with its laser beams. The ThunderCats are able to distract the robot just long enough for Tygra to reach his laboratory where he begins work on an antidote. At the same time, Lion-O makes his way to the Sword Chamber. Using the sword's sight beyond sight, Lion-O sees that the Mutants are already circling the lair in their flying vehicles.
Meanwhile Snarf, who had been out picking Candy fruit, arrives back at the lair only to be greeted by the Wolfrat's laser beams. Snarf pelts the robot with Candy fruit and runs away to join his fellow Cats. Panthro builds a suit of armor for Snarf and together the Cats attack and destroy the Wolfrat.
By now the Mutants have already entered the lair and are seeking to destroy the minute ThunderCats. Tygra finally succeeds in preparing the antidote and grows back to full size. He summons the other ThunderCats into his lab and they all return back to normal size. However, Snarf, who accidentally gets a whif of the antidote, grow to double his size and he alone is enough to handle the Mutants who flee for their lives.
Tired of Slithe's incompetence as a leader, Vultureman summonsRatar-O, hoping that he will succeed in defeating the ThunderCats. The two head off in Ratar-O's spaceship, the Ratstar, to the Planet of Snarfs and capture Snarfer, binding him in special shackles. They then head to Third Earth where Ratar-O assumes command of the Mutants, much to the chagrin of Slithe. He then lets Snarfer escape, knowing that he will inevitably lead the ThunderCats to him.
Snarfer runs straight to the Cats Lair where he meets his uncle Snarf who is delighted to see him. Inside the lair, Snarfer explains to the ThunderCats that when Thundera blew up, forty three of them commandeered an old Mutant tanker to an empty planet. As Snarfer is explaining about the Planet of Snarfs, Ratar-O pulls him to Castle Plun-Darr using the Rat's Eye to attract the cuffs that he put on Snarfer.
The ThunderCats set out after Snarfer in the ThunderTank, leaving Wilykit and Wilykat to guard the lair. Unbeknownst to them, they are driving straight into an ambush set by Ratar-O who uses the Ratstar's scramblers to disrupt the ThunderCats' communications including the Sword of Omens' "Sight beyond sight".
The Ratstar then attacks the ThunderTank, first firing the Barri-cannon at it and then turning a pile of rocks into a Rock Giant using the "Molecular Mutator". The ThunderCats manage to overcome all of these until Ratar-O fires the Void Charges which hit the tank and damage its main thruster. As Panthro tries to repair it, Lion-O distracts the Ratstar by drawing its fire towards him. He uses the Sword of Omens to counter the ship's fire and finally fires a beam from the sword which damages the Ratstar, causing it to crash. Having defeated the Mutants, the ThunderCats head to Castle Plun-Darr and free Snarfer.
Back at Cats Lair, Panthro and Lion-O are finishing their newest vehicle, the Feliner, which will enable the ThunderCats to travel into space. However, Panthro explains that without a "Hyper Space Mega Condenser", the spaceship will not be operational. Snarf then suggests that they obtain the part from the wreck of the Ratstar.
The Mutants emerge from the wreck of the crashed RatStar andSlithe blames Ratar-O for their failure to defeat the ThunderCats. He goes so far as to challenge Ratar-O's authority, a move which greatly annoys Ratar-O and he immediately uses the power of his Rat's Eyesais to put Slithe and the other Mutants in their place. He then instructs them to build a Mutank from the wreck of the RatStar and they use it to drag the wreck to Castle Plun-Darr.
Inside Cats Lair, Snarf is contemplating leaving with Snarfer for the Planet of Snarfs but doesn't reveal his thoughts to the others just yet. He only tells Snarfer about his intentions and the two join the rest of the ThunderCats as they head out in the ThunderTank to obtain the "Hyper Space Mega Condenser from the wreck of the RatStar. Meanwhile, Mumm-Ra, who had been observing the activities of both the ThunderCats and the Mutants from his cauldron, decides to seize the Mega Condenser himself in order to lure the ThunderCats to him. He changes to his ever-living form and flies out of hisBlack Pyramid.
As the ThunderCats reach the wreck site, they are surprised to find the RatStar missing. Lion-O uses the Sword of Omens' "Sight beyond sight" to see that the Mutants had towed the wreck to Castle Plun-Darr, so the ThunderCats head there. As soon as they reach Castle Plun-Darr, the Mutants, led by Ratar-O, attack the ThunderCats using the Mutank. As the two tanks engage in battle, Lion-O slips out and enters the wreck of the RatStar to try and locate the Mega Condenser, only to find it in the possession of Mumm-Ra.
Mumm-ra flies out with the Mega Condenser but Lion-O snags Mumm-Ra's cape using his Claw line and he too is dragged out. Lion-O then pulls Mumm-Ra to the ground, causing him to drop the Mega Condenser. Seeing that he is no match for the Sword of Omens, Mumm-Ra retreats. Before Lion-O can get the Mega Condenser, Ratar-O reaches it and challenges Lion-O to a duel over the right to its ownership. The Rats Eye and the Eye of Thundera clash in a fierce battle but the Sword of Omens proves to be the more powerful one and Ratar-O flees. The ThunderCats collect the Mega Condenser and head home.
Back at Cats Lair, Panthro, Cheetara and the ThunderKittens are getting ready to take Snarfer to his home planet in the now operational Feliner. At that point, Snarf reveals his decision to leave with Snarfer, claiming that he isn't need anymore. This greatly shocks and saddens the ThunderCats, especially Lion-O who pleads with Snarf not to go but Snarf does not relent. The Feliner takes off but moments later returns and Snarf, having decided to stay after all, runs out of the spaceship and into Lion-O's arms.
While out on a routine space patrol in the Electro-charger, Mandora encounters an old space freighter which does not meet the inter-galactic standards. She boards the ship for inspection. Finding only its captain on board, she instructs him to land the ship on the Gray Prison Planet for further inspection.
Meanwhile, Lion-O and Snarf who had been monitoring Mandora from Cats Lair, recognize the old space freighter as being the Jolly Rogers, the pirate ship of the notorious Captain Cracker. They warn Mandora but Captain Cracker and his robot crew lock Mandora in the control room and begin taking control of the Gray Prison Planet, opening the cells of all the prisoners incarcerated there.
Mandora sends the Electro-charger to Lion-O via remote control and he rides it to the Gray Prison Planet. As soon he arrives there, he is attacked by the hulking Rhino, one of the convicts released by Captain Cracker. Luckily, his old acquaintance Quick Pick appears and helps him lock Rhino in one of the prison cells. They then rush off to find Mandora.
In another part of the Gray Prison Planet, Captain Cracker has Mandora tied up on top of a giant pot of boiling oil. As he begins lowering her into it, Lion-O and Quick-Pick arrive just in time to save Mandora from being boiled alive. Mandora and Quick-Pick escape but Lion-O gets caught by Captain Cracker and his cronies. They ties him up, blindfold him and make him walk the plank into outer space. Just as Lion-O steps off the plank, Mandora and Quick-Pick catch him in the Electro-charger.
Captain Cracker sails his ship to Third Earth with the intention to attack Cats Lair. Lion-O uses the Sword of Omens to summon and warn his friends about the impending danger. The ThunderCats set off in the ThunderTank to intercept the Jolly Rogers as it lands in a nearby river. As soon as Captain Cracker and his robot companions emerge rom their ship,Panthro fires a net from the ThunderTank and succeeds in capturing all of them. Mandora later arrives and takes all the prisoners back to the Gray Prison Planet.
Wilykit and Wilykat are enjoying themselves, picking apples in the forest. Mumm-Ra, who is observing them from his cauldron, is extremely annoyed that the ThunderCats are thriving on what he claims to be his planet. He summons the Driller and pays him diamonds to bore an underground hole from Acid Lake to the Cats Lair. The Driller complies by burrowing the channel and at once the lake's powerful Ultrasolvic acid starts dissolving the Cats Lair's foundation.
Unaware of the grave danger that they are in, the ThunderCats are carrying on their daily activities as normal inside the lair. As Snarf prepares apple sauce using the apples that the ThunderKittens plucked, the adult ThunderCats are testing out a new "Super fuel" invented by Tygra for the ThunderTank. Suddenly Lion-O detects a foul odor in the lair. Tygra puts the emanation through the analyzer and identifies it as being Ultrasolvic acid. Lion-O uses the Sword of Omens "Sight beyond sight" and discovers that the acid is right under the lair. Tygra suggests that the only substance that can neutralize the acid is Sponge Fog, and so the ThunderCats rush to obtain it.
The ThunderTank soon reaches the valley where Sponge Fog grows. Panthro engages the tank's cutters and carves out a block of the Sponge Fog. As the ThunderCats start to tow the Sponge Fog, Rockmen start pelting the tank with giant boulders from the top of the cliffs. In order to avoid the shower of boulders, Panthro decides to take a detour through theForest of Giant Insects.
As soon as they enter the forest, the ThunderCats first encounter the Mechanosect and then a giant beetle but the Cats manage to vanquish both the bugs. The tank then abruptly stops due to a fault with its transmission. Lion-O exits the tank to inspect it but is immediately seized in the mandibles of a giant worm. As the worm begins to burrow into its hole, Lion-O manages to grab his sword and summon the other ThunderCats. Panthro, Tygra and Cheetara attack the worm and it lets go of Lion-O.
Seeing that the ThunderCats had successfully overcome all the obstacles that they had faced, Mumm-Ra decides to delay them himself. He transforms into his ever-living form and flies out of his Black Pyramid. By now, the ThunderCats have reached the Bridge of Light and as they start to cross it, Mumm-Ra flies in and destroys the bridge. The ThunderTank falls into the River of Despair below. After almost being sucked into the Whirlpool of Infinity, the ThunderCats manage to reach the Cats Lair just in time to plug the hole in the foundation with the Sponge Fog and save their home.
An apparition of Wizz-Ra, an ancient Egyptian sorcerer, appears in the mirror in Cheetara's room, waking her from her sleep. While initially wanting to tell the rest of the ThunderCats about this strange occurrence, Cheetara decides against it, fearing that they might not believe her.
Meanwhile, Mumm-Ra watches Cheetara from his cauldron inside the Black Pyramid and explains to Slithe that Wizz-Ra possesses the Enchanted Golden Helmet of Pharnoor. The helmet gives its wearer the power to control minds. He recalls how many centuries ago he had tricked Wizz-Ra into getting banished and imprisoned in the Seventh Dimension for all eternity. However, once every seven thousand years, Wizz-Ra is able to return to Third Earth for one single day via a portal which coincidentally happens to be on the exact same spot as the mirror in Cheetara's room.
Mumm-Ra then brings the Fatatah Cheetah statue in his pyramid to life using his powers. He instructs the feline to bring him the enchanted helmet. The cheetah speeds to the Cats Lair and, avoiding detection, climbs into Cheetara's room and enters her body. At that moment, Wizz-Ra emerges from the mirror and the Fatatah Cheetah lunges on him. The cheetah then grabs his helmet and takes it to Mumm-Ra.
Inside Cats Lair, Lion-O and Snarf are unable to wake Cheetara from her sleeping trance. Wizz-Ra explains that she is under Mumm-Ra's power and only if he had his helmet could he break her trance. Thus the trio immediately head to the Black Pyramid. Once there, Mumm-Ra uses the enchanted helmet on Lion-O and starts taking control of his mind. Lion-O uses every ounce of his strength to summon the other ThunderCats before completely falling under Mumm-Ra's control.
Mumm-Ra orders the entranced Lion-O to throw the Sword of Omens into the Desert of Sinking Sands where it disappears without a trace. Lion-O then attacks Wizz-Ra but the sorcerer uses his magic power to stop Lion-O in his tracks. Shortly after, Panthro, Tygra, Wilykit and Wilykat arrive and they all fall victim to Mumm-Ra's mind control. Like Lion-O, they too attack Wizz-Ra and again he uses his magic to subdue them. After expending so much of his power, the weakened Wizz-Ra and Snarf retreat back to Cats Lair.
Outside the lair, Wizz-Ra and Snarf encounter Cheetara, who has broken free of Mumm-Ra's control. The three then head back to the Black Pyramid and sneak inside it undetected. While Mumm-Ra and Slithe are gloating over their success, Cheetara quietly moves the Vulture King statue so that the sun's beam coming from the roof hits its left eye. This fools Mumm-Ra into thinking that the day is over and Wizz-Ra has returned to his dimensional prison and so he removes the helmet. Snarf quickly grabs the helmet and gives it to Wizz-Ra who uses it to free the ThunderCats from Mumm-Ra's control and then blasts Mumm-Ra with his magic, causing the mummy to retreat into his sarcophagus.
With the day almost over, Cheetara helps Wizz-Ra to get back to the portal before time runs out for him. Wizz-Ra then thanks Cheetara and bids her farewell before entering the mirror and returning to his dimension. Lion-O calls the Sword of Omens and it emerges from the sands and flies into his hand.
Witnessing unusual activity in the Kingdom of Webs from his cauldron, Mumm-Ra summons Nemesis to explain this phenomenon to him. The force of darkness informs Mumm-Ra that the Kingdom of Webs has a newly hatched queen called Spidera. Mumm-Ra then transforms into the tiny Diamondfly in order to lure the ThunderCats into Spidera's web of rage.
Outside Cats Lair, Lion-O is lazing in the grass when he hears cries for help. When he goes to investigate, the Diamondfly mesmerizes Lion-O into a trance and starts leading him towards Spidera's lair. When Snarf, who had just emerged from Cats Lair, notices the Claw Shield and the Sword of Omens lying unguarded, he knows something is terribly wrong. He picks up the two items and goes off in search of Lion-O. Snarf finds Lion-O deep in the forest, still under the Diamondfly's spell, but manages to snap him out of his trance. Back in his senses, Lion-O uses the Sword of Omens to expose the Diamondfly for who she really is, Mumm-Ra. Unfortunately, Snarf gets caught by a spider who drags him underground. Lion-O goes after Snarf and finds himself in the Kingdom of Web where his beloved nursemaid has been trapped in a cocoon in a giant web.
As Lion-O tries to free Snarf, Spidera appears and Lion-O immediately summons the other ThunderCats. While waiting for his friends to arrive, Lion-O valiantly battles Spidera but eventually gets the Sword of Omens knocked out of his hand. Spidera then flings Lion-O into one of her giant webs where he becomes stuck and unable to move.
At that moment, the ThunderCats crash into Spidera's lair in the ThunderTank. Panthro, Cheetara and Tygra all attack Spidera while at the same time trying to get the Sword of Omens to Lion-O. However, Spider proves to be too strong for them and one by one they all end up being caught in her steel-like webs. Tygra manages to throw the sword to Snarf who catches it with his tail and flings it to Lion-O.
Lion-O grabs the sword and frees himself from the web. Seeing their lord in action gives all the other ThunderCats the power to break free of their web bindings. With a renewed vigor, the ThunderCats attack Spidera again, this time succeeding in defeating her.
Inside Cats Lair, the ThunderCats receive a distress signal from the space-liner Vertus which is in the Sea of Stars, six light years from Orion. Lion-O, Cheetara and Snarf take off in the Feliner to assist the space-liner.
They soon reach the enormous spaceship, Vertus, which is drifting right on the edge of a Black Hole. Lion-O and Snarf board the ship but do not find anyone on board. While exploring the ship, they come across cups of hot coffee laid out on a table. Lion-O takes a whiff of one of the cups and immediately loses consciousness. Snarf also passes out by inhaling the fumes from the spilt coffee. At the same time, the Feliner gets fired upon by laser beams from the Vertus but Cheetara manages to avoid them and zooms away back to Cats Lair to get help.
When they regain consciousness, Lion-O and Snarf find themselves prisoners of the ship's captain, Shiner, who is now in possession of the Sword of Omens. Just then, Mumm-Ra materializes and reveals that it was he who hired Shiner in order to obtain the sword. Mumm-Ra then casts the sword into the Black Hole after which Shiner's crew chain Lion-O and Snarf in the reactor room of the ship and force them to pull Boron rods.
Meanwhile, Cheetara returns in the Feliner with Panthro and drops him on the Vertus. Panthro sneaks into the spaceship and frees Lion-O and Snarf from the reactor room. The three then neutralize Shiner's crew and take over the ship. Panthro then sets the course for the Black Hole, much to the shock of Captain Shiner.
The Vertus enters the Black Hole which turns out to be a giant force field, filled with debris of old spaceships and satellites. They then come across a super power station which is controlled by a computer known as NEPTUNE, the Navy Engineers Power Tower Under Nuclear Energy. The artificial intelligence imprisons the ThunderCats and Shiner in an impregnable Titanium room.
Just when all seems lost, Jaga appears and reminds Lion-O that the Eye of Thundera only sleeps until needed. Lion-O then summons the sword to his hand and uses it to break out of their cell. Panthro reverses the magnetic polarity of the power station before he Lion-O, Snarf and Shiner board the Vertus. The reversal of the magnetic force causes everything to be repelled out of the Black Hole including the Vertus. As the ship emerges from the Black Hole at break-neck speed, it hits an asteroid which badly damages it. Shiner orders the three ThunderCats to abandon ship while he chooses to go down with it. Luckily, Cheetara spots them and picks up Lion-O, Panthro and Snarf in the Feliner. While the ThunderCats assume that Shiner perished with his ship, he is shown to have escaped safely in a smaller spaceship.
Wilykit and Wilykat find a magic harp containing a genie. His name is Charr-Nin.
Mumm-Ra offers to free the genie if he helps to destroy theThunderCats. Foolishly, Charr-Nin agrees, and begins trapping the Thundercats in his lamp one by one. Mumm-Ra's plan works, and he betrays Charr-Nin.
During their arguing, the Thundercats manage to escape, leaving Mumm-Ra and Charr-Nin battling beneath the earth.
On Lion-O's 20th birthday, he must pass a set of trials to become the true Lord of the Thundercats. Even though he is the hereditary Lord of the Thundercats, he has not proven himself to be worthy of that title. Lion-O must prove that he is he lord of the Thundercats by facing his friends and fellow Thundercats alone and unarmed.
His first test is to beat Panthro in a duel to test his strength.
The Demolisher is a brown rottweiler-looking space traveler who is driven only by the desire to fight and destroy. He is accompanied by his side-kick and cheerleader, Dirge . He landed on Third Earth to challenge Mumm-Ra to a fight. The Demolisher is victorious against Mumm-Ra and sends him running back to his Tomb. Mumm-Ra acknowledges the power of Demolisher, and convinces him to seek and destroy Lion-O. The Demolisher, searching for another fight, gladly accepts Mumm-Ra advice. He battles with Lion-O only to face defeat and flee in shame from Third Earth.
Monkian goes to Mumm-ra and agrees to give him anything if Mumm-ra will make him powerful enough to rule Third Earth. Mumm-ra agrees cleverly, and gives him Power Spheres which make him super strong and give him super weapons. He freezes all the Thundercats, then defeats Lion-O and takes the Sword of Omens back to Mumm-ra. Mumm-ra takes it, and then says that Monkian's part of the bargain will be that he can keep the spheres, but he has to stay in Mumm-ra's pyramid for all eternity.
The walls start to surround Monkian, and every time he breaks them down, a new set of walls shows up. While Monkian and Mumm-ra are arguing, Lion-O retrieves the sword and frees the other Thundercats. Monkian gives up his power to be free again.
After the Mutants fail to ambush and defeat the ThunderCats with Vultureman's new Thundrainium Cannon, Vultureman, furious about the failed attempt and the loss of his weapon, activates a self-destruct built into each of his inventions or repaired machinery, and all the Mutant technology disintegrates. To even the odds, Slithe asks Mumm-Ra to send an electrical energy creature to destroy all the equipment in Cats Lair, which also seals up the door to the Sword Chamber, trapping the Sword of Omens inside along with all the Thundercats' weapons.
The Mutants attack, and manage to capture Cheetara and Panthro. Snarf must climb into the ventilation shafts to reach the Sword Chamber from within, but Jackalman follows him trying to capture him. Outside, Lion-O is attacked by Slithe and Monkian, and later Mumm-Ra. After Snarf successfully gets the Sword back to Lion-O, Lion-O summons Panthro and Cheetara (freeing them) and they defeat Mumm-Ra and the Mutants.
Micrits, a tiny race of human like figures happen to live right outside Cats Lair. Unaware of their existance, Lion-O manages to continuously step on their village (keep in mind they are the size of toy figures) and destroy their homes. Upset at this disrespect, the Micrits decide to take a stand and manage to trap Lion-O and later steal the Thundercats' weapons from Cats Lair. With the ThunderCat Lord in trouble, the mutants attack Cats Lair. After much talk, Lion-O manages to convince the Micrits that he's good and convinces them to let him go to help save his friends. Once again, Lion-O saves the day, and befriends the Micrits. Afterwards, the ThunderCats mark the location of the Micrits' territory on their maps and in the field, and take alternate routes to avoid passing through it.
On the second day of his trails, Lion-O must raceCheetara through the dangerous lands of third earth. Although Cheetara is by far the fastest among the Thundercats, her speed can only last for a short time period. After that, she runs as fast as any other cat. Lion-O takes a shorter, but more dangerous route to make up for Cheetara's advantage.
A volcano bursts from out of nowhere, releasing the beast known as the Rock Giant. The Rock Giant is a powerful monster made entirely out of stone. Mumm-Ra decides to use the giant to destroy the Thundercats. While this is all happening a storm happens due to the erruption which has the left the Thunderkittens trapped in a forest.Lion-O and Panthro attempt to rescue them but before they can do so Jackalman attacks the thunder-kittens in one of the skycutters. The Thunderkittens are able to defeat Jackalman by using their magic pellets and summoning a flying saucer which causes Jackalman to grab ahold of the Skycutter. Thinking it's hostile, the Thundercats shoot the Skycutter and cause the Thunderkittens to barely be shot out of the sky.
The Thundercats leave in their Thundertank and attempt to arrive back at their lair, but are stopped by the Rock Giant who is pursuing the machine. Lion-O, Panthro, and the Thunderkittens are able to escape from the tank before the rock giant nearly destroys it. The Thundercats attempt to face the Rock Giant but find that their weapons aren't working. Eventually Lion-O is able to persue the beast to face him alone.
Durning the fight Jaga appears and tells Lion-O to remember how the ancient one used the power of heat to break even the hardest of rocks. Lion-O is able to use the Sword of Omens to push the giant to some white heat. He then lures him into the cold water near the lair's moat. The temperature destroys the Rock Giant.
Jackalman decides to start his own army in the hopes of conqueringThird Earth by himself. He does manage to give the Thundercats trouble, but soon he is defeated and ends up crawling back to the other mutants at Castle Plun-Darr, who aren't very happy that he rebelled in the first place.
An evil robot monster is attacking the Tuska Village in an area unexplored by the Thundercats. Turmagar, the leader of the Tuskas, travels to the Cat's Lair to ask for aid in defeating the Technopederobot which is destroying his village. The Thundercats agree to help Turmagar, and set out to the Tuska Village.
Lion-O must outwit Wilykit and Wilykat in the Maze of Infinity, but there are more than ThunderKittens lurking about who are ready to stop him.
The pair set traps in the maze. However he manages to avoid their traps. In order to beat them through the maze, Lion-O turns their own tricks back on them, and tricks them into losing the race through the maze.
Mumm-Ra disguises himself as an innocent Berbil to try and defeat the ThunderCats. He plays upon their altruism to gain entrance into the Lair. Once inside, he casts a spell on them and, seizing them with slave bracelets, he transforms them under his command. Mumm-Ra's plan almost succeeds, when only Lion-O is left unaffected by the spell. Lion-O chooses not to use the Sword's powers against his fellow ThunderCats, because he believes in their ability to remain true to their real identities. Instead, he flees in order to fight Mumm-Ra alone with the Sword of Omens. In battling him, Lion-O calls forth the Sword's power. His faith in the ThunderCats proves well-founded, because their response to the Sword's emblem is stronger that Mumm-Ra's spell, and they free themselves from the spell. Returning to Lion-O's aid, they help him defeat Mumm-Ra.
What a person is really like is based on his personalities, which are his characteristic patterns of behavior and modes of thinking in reacting to the environment. Lion-O was tested when the other ThunderCats turned against him. But because his friendship was based on his knowledge of his friends' true personalities and not on superficial characteristics, he did not lose faith in them. If we choose our friends in this way, we can believe in them in times of crisis or when we hear misleading things about them, because we will know what they are really like. And because personality tends to be consistent over time, if we choose friends carefully, we can expect our friendships to last and be rewarding over a long time.
Panthro invents flying video cameras which are suppose to record the events that take place on third-earth so they could create their own holographic time capsule. Mumm-Ra, in the hope of destroying the Thundercats once more, revives the great mechanical monsters which the Thundercats have destroyed in the past and has them attack. He revives the Mutant Warbot, Driller, Mechanosect, and theTechnopede.
When a big storm hits Third Earth, the Thunderkittens are trapped in an old space capsule. Meanwhile, Tygra and Cheetara almost crash the Feliner, but Lion-O guides them in for a safe landing with the eye of Thundera. The kittens are captured by Mumm-ra, but end up saving the day by showing him his reflection in the window of the capsule.
The scene changes to Hook Mountain, where Lion-O must beat Tygra at a test of mind power. The Tiger Clan on Thundera were given special mind powers that enable them to produce illusions to their enemies. Lion-O must be able to distinctly separate the real from the unreal. Lion-O is clever enough to see past Tygra's illusions, and is able to earn his Thundercat insignia during fourth day of his trials.
The Ancient Spirits of Evil show Mumm-Ra the story of King Arthur, and explain to him that the strongest sword that ever existed was Excalibur, Arthur's weapon. Mumm-Ra disguises himself as Arthur, and returns to the lake where the sword is guarded by The Lady of the Lake. Fooled by his disguise, The Lady gives Mumm-Ra Excalibur.
The disguised Mumm-Ra challenges Lion-O to a dual, and Lion-O foolishly accepts the challenge. The swords clash, and Excalibur is victorious. The Eye of Thundera is split in two, and the Thundercats become powerless. Merlin, Arthur's teacher and a famous magician stops Mumm-Ra from destroying the Thundercats, and restores the eye to its original state
An old iceberg on Hook Mountain begins to melt, releasing an ancient being known as the Ice King who had been trapped in it for a thousand years. He begins to destroy Snowman's castle at the top ofHook Mountain. The Snowman tries to stop him but is frozen solid by the Ice King. Snowmeow, his faithful companion, seeks out Lion-Obut upon his arrival on Hook Mountain, he too is frozen solid by the Ice King. Panthro, Tygra and Snarf arrive in the ThunderTank but they too meet the same fate. Only Cheetara is left and she arrives just in time to place the Sword of Omens in Lion-O's hands, freeing him and he in turn frees the rest of the Cats and the Snowman.
After a brief battle with the Ice King, the Cats realize that he is not evil and is just trying to get into the castle to find an ancient egg which has an image of his wife. The ThunderCats help to obtain the egg from the Pterodactyl guarding it and give it to the Ice King. After taking one last look at the image of his queen in the egg, the Ice King melts away.
Two aliens arrive in spaceships and fight near Cats Lair. Lion-Oquickly encounters the two beings, a Kymera and a Terator, who each tell him the other's race is evil and cannot be trusted. Unfortunately, he makes the mistake of assuming that the more attractive of the two is the one he should side with.
Eventually the deception is revealed. After realizing his mistake, Lion-O summons the rest of the Thundercats who arrive in theFeliner to defeat the true villian and help out the other alien.
A spaceship approaches Third Earth and it sets off all the alarms of the Thundercats, Mutants and even Mumm-Ra. It contains enough radioactive material to put an end to the Thundercats. Jackalmantakes the recovered materials first and Mumm-Ra takes it from him. The Thundercats battle Mumm-Ra on top of the Black Pyramid for the sphere and eventually win, setting the materials to explode safely in space.
Vultureman invents a voice imitator which can imitate (anyones) voice. The mutants use the invention to trick the Thundercats into falling for false distress calls. They go on the communication frequency that the Thundercats use and pretend to be Thundercats in danger.
Each Thundercat is lured into a different danger zone of third earth.Wilykit and Wilykat get trapped in the Vortex, Cheetara in a giant bee hive, Tygra in Mole-masters hole, and Panthro gets captured by the mutants. Lion-O and Snarf go off to save them once again, and put the mutant scheme to an end.
Mumm-ra transforms himself into the Dream Master, and gains the power to control the Thundercats' dream selves. All except Lion-O. They all become slaves to Mumm-ra the Dream Master in their sleep, but when they wake up, they are just tired. However, when the Thundercats sleep again, Mumm-ra captures their dream selves in little bottles, and when Lion-O tries to wake them up, he can't. He goes and fights Mumm-ra, and frees the other Thundercats' dream selves. They wake up, come running, and help to defeat Mumm-ra again.
Willa is captured by the Mutants, and Tygra and Nayda, Willa's sister, must go to Castle Plun-Darr to save her. Tygra uses the invisibilty power of his whip on both of them, so they could sneak into the castle and rescue Willa, but having 2 people at a time takes too much power from the whip, so they are stuck being invisible. Lion-Ouses the Sword to make them visible once again and Willa is rescued.
Lion-O takes up mountain climbing, but during one of his climbs, theMutants attack him with a Thundrainium gun. Lion-O calls the other ThunderCats, but an avalanche traps Panthro, Tygra, Slithe, andMonkian in a cave causing a limited air supply. MeanwhileJackalman steals the Sword of Omens, but Lion-O manages to get it back and save everyone.
Vultureman invents a Super Power Potion, which gives him incredible magical powers and strength, enabling him to mesmerize and defeat Tygra. Vultureman then makes a deal with Mumm-Ra that he will share the potion in exchange for Mumm-Ra's secret to everlasting life. Vultureman asserts his authority over the other Mutants, putting Slithe in a trance. He attacks and defeats Panthroas the latter searches for Tygra. Slithe recovers and commands theMutants to search for the potion. As they discover it, Mumm-Ra materializes and confiscates the vial. Meanwhile, Vultureman challenges Lion-O and is about to defeat him when his super powers wear off. Mumm-Ra appears and denies Vultureman's plea for another dose of super power. Lion-O destroys the potion and Vultureman slinks away defeated.
Panthro makes a fake sword of omens, planing on playing a practical joke on the Mutants. But the joke backfires when the Mutants capture Snarf as well. Lion-O must rescue Snarf and defeat the Mutants and Mumm-Ra once again.
Finally, to prove that Lion-O is worthy to be the Lord of theThundercats, he must defeat his worst enemy. Mumm-Ra. He manages to find a way into Mumm-Ra's tomb, and defeats him by throwing his coffin into the evil cauldrum. This is the first time that Lion-O really defeats Mumm-Ra.
It's the moment of truth when Lion-O finally faces Mumm-Ra. Then Lion-O has to fights demons and other monsters then finally gets to Mumm-Ra. Lion-O for once not use his Sword of Omens and Power Claw, instead he used his fists, feet, and wits to win. In the end, Lion-O's hard work paid off and he has proven that he is not just Lion-O but that he is Lord of the Thundercats.
The Thunderkittens decide to steal the Thundercats' weapons so they can prove they can use them, but the Mutants steal the weapons in turn. Lion-O and the kittens must get the weapons back from the Mutants.
After a space battle with the Mutants, the group escapes in pods and land near a White Pyramid. Inside they meet Mumm-Rana, who isMumm-Ra's exact opposite. Mumm-Ra arrives and places her under a spell to control her, after falling in love with her and noting her knowledge of magic.
These two now evil Mummies plot to destroy the Thundercats and rule third earth side by side as King and Queen. However Lion-Opevails, and the Thundercats manage to turn Mumm-Rana back to her good self, and banish Mumm-Ra once again.
Vultureman creates a device that shifts minds and bodies. He givesPanthro Snarf's body, and gives Snarf Panthro's Body. He also shiftsLion-O and Wilykat, and thus makes the Sword of Omens unusable. Eventually, Vultureman shoots the sword, and it causes a reaction that restores all the Thundercats to their rightful bodies.
Under the guise of Dr. Dometone, Mumm-Ra lures Lion-O into a battle against four of his most formidable enemies Rataro, Safari Joe, and others in an attempt to eliminate the young ThunderCat.
Mumm-Ra takes Lion-O to a gallery of the ThunderCats accomplishments. However, the pictures can come to life and Lion-O must battle them. Once the other ThunderCats arrive they end up in trouble and Lion-O is confronted by Mumm-Ra who has made himself into a carbon copy of Lion-O. It's Lion-O VS Lion-O and the battle is a draw, until Lion-O shows Mumm-Ra his reflection.