Magus was accepted into the Hero tourney, so I'm going to have to bar him from villain. I view villains as anybody who doesn't permanently join the party, although I am allowing Mewtwo since he was pretty bad in the movies. So it's situational in that aspect, but good rule of thumb.

Sure, I'll allow Byakuya.

Oh, I'm ruling Avada Kedavra to be like "Power Word: Kill" in Dungeons and Dragons. It won't work on people who are REALLY strong unless you knock down their "hp" (in this case, injure them), but if they're injured enough it will not fail.