The Phantom Dust aura in question:
More of a glow, really. Slight Akuma/Demitri energy flow would be added, but only if I can figure out a way to make it not double the SFF while still being alpha blendable. The V-ism shadow idea mentioned above paired with an energy aura effect helper rendered behind the sprites? I'm close to abandoning the aura idea entirely, minus supers. Supers would be an acceptable place to have a bunch of unique aura sprites, I think. It'd convey just how super the moves are. Or something.