Omega Gaster or some GB!AU Gaster where he turns into a skeletal Firhaur.

His wing membranes aren't really... there until he starts flying, at which point they're like a thin, slightly purple, glowy film between the fingers.

His ribcage is also full of some strange Magic glowy stuff. It's slightly purple, as well.

I can't decide if he could just shoot the classic Blaster beam from his mouth, or actually breathe fire (of the purple, Magic variety, of course). Maybe he can do both.