Oh he doesn't have any markings those are parts of his shadows. The ShadowCrafter can call on darkness where there is none. The shadows he creates can be shapless and mistlike or they can manifest into something solid. He can become shadow himself (in whole or in part)and so it is as much a weapon as a defense.
You see only what he wants you to and does not need to manifest even a part of himself to kill you once you're inside it (you'll have to read the book to find out how).
He is the most feared vampire to ever live.