Mumm-Ra is weak and faces the threat of three new Thundercats, so he sends the Mutants to release his old enemies the Lunataks from their imprisonment in order to bolster the forces of darkness.

The Mutants succeed in releasing the Lunataks, who immediately begin looting Thundrillium and taking slaves from the local villages, leading to their first run-in with the Thundercats.

The Thundercats build the Tower of Omens to monitor for new and dangerous enemies. Meanwhile, Ma-Mutt, disguised as a Berbil, spies on the Thundercats.

Mumm-Ra's power is restored, and Snarfer makes it to Third-Earth but crashes in the Lunataks territory, leading the Thundercats to rush to find him before they do.

In searching for the Lunataks flying fortress Sky Tomb, the Thundercats discover that Mumm-Ra is alive again and more powerful than ever before, leading to an epic battle between him and Lion-O.

Mumm-Ra takes the form of Jaga and creates dissent within the ranks of the Thundercats, causing them to fight each other.

The Lunatak Alluro uses a powerful talisman on the Thundercats that takes away all their self-confidence, leaving them hopeless and confused.

In his latest evil scheme, Mumm-Ra plans on using the legendary Mask of Gorgon, an artifact which turns all to stone, against the Thundercats.

After venturing into a remote cave on Hook Mountain in search of Thundrillium, the Lunataks and later the Thundercats fall victim to a bizarre entity with the power to expand upon the negative influences in a person's soul.

Mumm-Ra summons the Berserkers and coats their armour in Thundrainium and sends them to assault the Thundercats at the Tower of Omens.

Ravage Island is an island on Third-Earth with a powerful beacon on it that can control minds. Mumm-Ra seeks to use the beacon to make the Thundercats his slaves.

Thanks to an unfortunate mishap with a time capsule, Lion-O rapidly grows younger and younger. His fellow Thundercats must reverse the process before he ceases to exist.

Vultureman builds a powerful sonic gun with a sound stone he steals from the Lunataks territory of Darkside.

The day of the eclipse arrives and any spell Mumm-Ra casts will last until the next eclipse. He casts a spell of decay on the Cats Lair, causing it to fall apart.

Chilla freezes Snarfer's spaceship as he heads back to the Tower of Omens. When Mandora gets involved, Chilla freezes her and becomes a fugitive from the law.

Luna discovers that her grandmother's magic belt is in the possession of Mumm-Rana and heads straight for the Pyramid of Light to claim the artifact and greatly increase her own power.

Luna tricks Hachiman and steals his sword, the Thunder-Cutter, and gives it the Lunataks new samurai robot, the Automaton.

Feeling neglected, Wilykat and Wilykat decide to run away to teach the rest of the Thundercats a lesson. However, thanks to Mumm-Ra, not all goes according to plan.

When all of the Thundercats except Lion-O are gone, Mumm-Ra switches Snarf with Ma-Mutt, who gives Lion-O poisoned candy fruit.

Vultureman builds a devastating device called the Thundranium projector which Wilykat and Wilykit manage to ruin. In return, he damages their space boards, putting them in major peril.