Skeletor finally does something relatively smart: why go to Grayskull when Grayskull can come to you?
With the Sorceress out on a mission, Skeletor takes the opportunity to literally bring the castle to where he is, in the Shadow Lands. The heroes follow, and after a brief fight on top of Grayskull, Skeletor's magic is turned against him and he is teleported away.
Grayskull fades away and returns to its original location, and Skeletor's hold over the Shadow Lands is gone, returning it to a colorful landscape.
Scans courtesy of Black.