Etrigan the Demon is an antihero and occassional superhero in the DC Universe.
Origin
He was a knight in Camelot and in that time it was under attack from the king's sister Morgan Le Fay and Merlin the master sorcerer tried to help but he saw there was a great disadvantage so he took one of the knights: Jason Blood and released his inner demon: Etrigan who helped them win, but nevertheless Camelot fell.
TV shows
He comes out in an episode of Batman the Brave and the Bold and in an episode of the justice league
Powers
Turns into Etrigan by saying this: GONE FORM OF MAN, RISE THE DEMON ETRIGAN, by saying inferno he breathes fire is immune to fire, super strength and can go to hell