So... it... just kills itself?

Fits in with thrull theme. Also, you automatically get your opponent to sac something before you lose him, so at worst it's an innocent blood.

So much negative synergy with the rest of black as drawing is a minor theme. This would probably be a lot better as a mythic if it was restricted to opponents only. You can increase the cost proportionally if its too powerful.

Black has a token/sacrificing theme, not a drawing theme.

I can see this guy being pretty neat if he said non-Demon.

non-Demon would be pretty broken. As is he helps further a theme in black and becomes more appealing to johnnies.

As a resident Johnny, this card makes me anxious to play him. Never mind the sacrifice of useless creatures, I want to pack cards like Vision Skeins, Forced Fruition and Words of Wilding.

I like the way you think :)

Non-demon wouldn't really be broken. To avoid saccing stuff yourself this guy would likely have to be your only creature, and, well, a 6/6 mythic for 5 that says "Cast ~ only if you control no creature" probably isn't broken. Also compare Rakdos the Defiler.

Ha! I like it. It would normally be a benefit, but it's kind of funny that you could get stuck with this Demon on the board and no way to get rid of him. Demons are mean like that.

I'm not sure whether it's good or not, but I always think "non-demon" is hilarious :)