Skeletor had long been a threat to Eternia as he would constantly try to invade Castle Grayskull and take its power for himself. Things began to look up for him when Eternia fell into his grasp.
However, his attempt to capture the Angels of Disney and Phantom resulted in him getting sealed away in another dimension.
Chronicles of the Children of Megatron
Skeletor is Darth Menslady's other adoptive brother.