In KH:3D there seems to be a new symbol, sorry don't have the picture, but it seems to be a mix of the Heartless and Unversed symbols, and since both creatures are made of darkness and negativity (negative energy), then I'm assuming that maybe we will see a creature created from pure darkness or something purer than that, pure energy, or something, maybe the thing that forms the basis for heartless, unversed, and nobodies, who knows, within the RoD, maybe thats what the Red Eyed boss was. You can say it was a heartless but no one can say that for sure, plus why would they make the Secret Episode boss that they teased in trailers and magazine scans an ordinary pure blood heartless. Im just speculating, you can say theres enough new types of enemies, but theres only 3, and I say bring em on, they need more diversity in Kingdom Hearts then three types of creature, now only two since theres no more Unversed. Some say its the symbol of the Mark of Mastery, but why would that symbol be a mix between two enemy symbols doesn't make sense, and its not the symbol on Aquas chest.