I'm interested in joining in for this, as I find these games a blast, even though the ones I'm in tend to just... stop.
Anyways, here's my sample, let me know what you like or would like different.
Costume: Black Mage Evilwizardington
Pre-Personality: Quiet, thoughtful. Cynical, sarcastic, and snarky. Easy-going, hardly takes anything seriously. Generally Chaotic Good, though he has some evil in him and a mean temper.
Shift-Personality: Lost some of positive aspects of personality. He's not as quiet and thoughtful, and loses some of the niceness that makes his cynisism, sarcasm, and snark tolerable. Is more evil and has an even worse temper.
Appearance: A little under six feet tall. Clad in the blue robes and yellow pointy hat of the black mage, his head is a shadow with two glowing yellow lights for eyes. It is impossible to describe what he would look like without his hat. The words don't exist, and if they did, you wouldn't understand them and they'd just drive you crazy anyways.
Abilities: Arcane magics of all sorts. Typical spells are Magic Missile, Shield, Sleep, Fireball, Lightning bolt, and much more. He also has a unknown number of daggers hidden in his robes, as well as a high proficiency in using them for stabbing.
Specific Spells And Feats can be listed as requested, and as they come into play.
Hadoken: Or perhaps Kamahameha? In any event, this is his most destructive spell, capable of wiping out a whole city. Not something to be used lightly. Or at all, as he's not able to draw on the power needed to use it. At least, not now.
Weaknesses: As many deptictions refer to wizards in the gaming world, he's a glass cannon. High on the destructive output, physically frail. The only saving grace is that no matter the damage he takes, as befitting his main character status, it's very hard to actually kill him. Concidering how painful he finds this, he's not too happy about it.
His shift personality has a lot more evil in it, though this is somewhat balanced out by the laziness and ineptitude that comes with it.