Every time Mumm-Ra gets a hold of a magic artifact to restore his powers, the ThunderCats just smash it and turn him into a dinky skeleton again. Until today that is, because Mumm-Ra just remembered he's got the Ancient Spirits of Evil, and now he can get swole whenever he wants.

Freed from the Astral Plane, Jaga, ghost of the ThunderCats mentor, is now free to visit the Cats' Lair. Which means he can finally tell them why Thundera, their home world, exploded. It's story time.