Hell Devil
The scary Hell Devil first appeared in the manga in chapter 63. It's a huge building, completely featureless except for an open maw and a skin that seems to be on fire. The anime's rendition of him will undoubtedly be eagerly awaited.
Hell Devil's alternate form is a huge hand with six fingers that appears from a portal in the sky. The Devil use this power in his efforts to damn souls. If it gets hurt in a fight, it simply needs a small amount of blood to heal. As of right now, Santa Claus and the Anti-Makima Squad are both on record as having signed contracts with the Hell Devil.