A three headed dog who belongs to Hades that guards the gates of the Underworld to prevent the dead from leaving. Cerberus was the offspring of the monsters Echidna and Typhon, and usually is described as having three heads, a serpent for a tail, and snakes protruding from parts of his body.
For more information see: JLA 80-Page Giant 2011
This version of Cerberus, he is a still three headed hound but instead of guarding the gates of Hell he guards the Circle of Hell meant for Gluttony. He also guards a piece of Dante's mask that he keeps in his stomach. When Booster Gold and Barbara Gordon find themselves in his circle, he attacks them. Booster flies down Cerberus's throat and get the piece so the pair can teleport away.