Mumm-Ra the Ever Living: The primary nemesis of the Thundercats, this slave to the Ancient Spirits of Evil has survived for thousands of years on Third Earth. He possesses incredible magical powers, and is also the wielder of the awesome Sword of Plundarr. His only weakness is a limited stamina; he needs often to return to his Pyramid to regenerate.

Monkian: He is a mutant with much brawn but little brain. He can maneuver easily admist the treetops, and wields a magic shield capable of firing cannonballs or energy blasts.

Slithe: Leader of the evil mutants on Third Earth. Killed by Mumm-Ra for one too many defeats.. he was later raised to serve him eternally.

Safari Joe:A ruthless intergalactic bounty hunter, Safari Joe is a malicious gamesman who came to Third Earth to hunt the most dangerous prey of all: Thundercats. He is armed with a versatile gatling gun capable of firing a various assortment of ammunition. His weakness is that he is a coward at heart, and relies too much upon his weaponry. Was killed by Mumm-Ra, for no other reason than he just needed killing.