Maxwell Hayes

The cultist ultimately responsible for Louis being a demon
Actually mauled to death by the time of the main stories, he only reappears as a hallucination. As realistic and sometimes physical he can get, he is at this point only how Louis perceived him (aka evil as all hell). He isn't a ghost, merely a presence.. a memory Louis holds in his mind

His hands are scarred by the cuts he's made for blood sacrifices. It takes a lot of blood to make a demon :-)