I'll vote Diabolus too. He's arguably the strongest one, so doing him first keeps the first battle from being too easy.
I have to make some minor changes to my character, but i'll post him here soon.

Edit: I wonder, what happens if one of our characters dies during the battle? Does he come back to life for the next?

Edit2: Drallinix, i just notice that your character can move "twenty times as fast as a normal man". That's a very vague way to state it. Does that mean 20 times sprinting speed of the average human? Cause that would mean he sprints at 200 mph at least.