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The Devil, being a Devil, is mischievous and likes to play practical jokes on all the other Guardians. He is proud to be from New Jersey and is inspired by all the great people who hail from the Garden State. He's aware that his appearance doesn't exactly scream "one of the good guys" so he goes out of his way to make sure people, especially kids, understand he is one.
Of course the evil villains the Guardians are up against know he's not someone to be messed with. He honestly enjoys confrontation and he's not afraid to jump into any situation with attitude. He's a bipedal humanoid with hoofed feet, a horse's head and the wings of a giant bat, reminiscent of the "Jersey Devil" from which he takes his name. He has the ability to withstand any heat and breathes fire. He doesn't merely defeat his opponents, he annihilates them. He has a whip-like tail that is comprised of flexible titanium and has barbed hooks at the end. In a fight there is simply no one better to have by your side.