The Nightmare King

The story's main antagonist. He was sealed behind a large door long ago, until Nemo, under Flip's misguided influence, accidentally releases him. He kidnaps King Morpheus in order to lure Nemo, and more importantly the Royal Scepter (which he and the other inhabitants of Nightmare Land fear), to his Nightmare Castle. Nemo barely manages to destroy the Nightmare King with the scepter and ends the evil king's reign along with Nemo's own nightmares.