This sounds a lot like HCL, another freeform, mega-crossover, sandbox rp I'm in, so I think I'll just jump in and do something. Let's see, who to use.....

Blackjack Pain, (real name Shane), a Kinetiscist who ended up here after defeating the Demon God known as the Black Prince. He carries the head of the Black Prince, and a part of it's soul, with him as a trophy.