'..because shape-shifting HURTS, you fool!'
I don't know where this came from - just a random doodle I suppose and a cry against magic transformations that just go 'pop' instantly when they should in fact involve lots of horrible pain.
Blackjack carries two magic rings: the Ring of Illusion and the Ring of Change. The former simply makes him appear human through a glamour spell, the latter actually changes his form. Black' prefers not to use either, but sometimes his usual appearance can prove 'inconvenient'.
He doesn't like to use the Ring of Change if he can avoid it, firstly because he doesn't like being removed even further from his dracoform than he already is, and secondly because the pain of having spikes sticking out through yer skin, muscles tearing and reforming and a pair of bloody great wings and a tail ripping out of your back etc etc tends to render one overcome with pain and therefore vulnerable.
edit - upon a mod's suggestion I've uploaded a bigger version so you can see it better!