He is one of the Beastfallen people who are born with the curse of a beastlike appearance and superhuman strength. Despite being mistreated in his life he has maintained himself as a better person. He has a gruff attitude but is in fact a very kind person. His name remains unknown as he was warned by Zero not to give his name out to witches who could use his name to control him. Since then he has been referred to simply as Mercenary.