[@Shoddy McCoy] Sorry, but with the absolute immense plethora of characters, worlds and stuff available, the answer is no to original characters and worlds. And ues, D-Links do need to be Disney/Square characters, because otherwise, it's not really Kingdom Hearts, is it?

Also, his Key does need to manifest in order to be used. There's nothing to stop him from using hand-to-hand speciality, like if it forms as a big-ass gauntlet or a knuckleduster or something. Also, do remember that Keyblades take form as a single item, so no dual-weilding until you have formed a second D-Link and got your second weapon.