He is originally a drawing from a magic book from Gideon Fisk. He was brought to life as a cartoon, it preyed on the main characters. But Fisk stubbed it with a dagger and it was dying. It tried to get back into the book, so it can never be destroyed, but one of the main characters threw the book into the fire, after that the monster disappeared into thin air.
It looks like a cartoonish version of a werewolf with yellow eyes and teeth.