Swamp Fox, Well what happens is you create a villain but then they're an NPC that I can use to tie into the story. So at this particular point I think its too early for his arch-enemies to show up. 

Poly, He was an East Coast villain so he's sweating it out on an island somewhere. But villains from all around the middle of the country ended up in that jail. But I can almost guarantee the dudes gonna show up. Also isn't the Schizoid Man insane? A tough prison isn't a good environment for that :P 

Maybe a guy who can project fear? Perhaps a somebody who can conjure weapons and has demonic mystical abilities? Ooh maybe a shadow controller.

Now I want to know who Xaxx is :P