Thanks for the tips, then. I guess I'll stat him up as a mage, then. Right now I'm imagining him as the campaign's "disc one final boss." I want to go for the angle that in the grand scheme of things, the Halloweeners aren't that dangerous, but Nightmare is.
EDIT: New idea. Nightmare is a chromed up beast, but he's also got a brain, and, more than that, he is aware. His magic is only 1, but he can perceive, and he knows how to make that an edge. He wants more, though, and believes that if he can get his hands on some tarot cards, he will be able to find a way to actually cast spells.