He is a sinner, so John Grace is correct, but he also answers to Sinner. Everything except his eyes is pitch black, and even he doesn't know why. His eyes are just large and round. He believes in God. He became a sinner by committing all the deadly sins (e.g., Sloth, Greed, Lust, etc. - what on earth did you do...). He has the appearance of an ordinary human and is very good at running away.