From Thundercats wiki
Mumm-Ra
Mumm-Ra the Ever-Living is an ancient, undead sorcerer and the primary antagonist of the ThunderCats who seeks to conquer Third Earth and destroy the feline refugees.
Origins and Powers
Mumm-Ra is a demonic entity serving the Ancient Spirits of Evil, residing within the Black Pyramid on Third Earth. While he typically appears as a withered, mummy-like creature, he can transform into a muscular, powerful form by reciting his iconic incantation. In this state, he possesses immense magical abilities, super strength, and the capacity to manipulate reality, making him a formidable threat to Lion-O and his companions.
Role in the Conflict
As the sworn enemy of the ThunderCats, Mumm-Ra is driven by a desire to possess the Eye of Thundera, the mystical source of the heroes' power. He frequently employs deception, dark sorcery, and alliances with the Mutants of Plun-Darr to undermine the ThunderCats. Despite his vast power, Mumm-Ra is bound to his sarcophagus; if he sees his own reflection, he is forced to retreat to his pyramid to recover, a weakness the ThunderCats often exploit during their battles.