Demodragon

Demodragon
Once the prized pet of Demogorgon, Prince of Demons, the demodragon now resides in the Nine Hells, where it serves as the gatekeeper of the Hellfire Games' final challenge.
Raised by vile magic from the corpse of a beheaded black dragon, the demodragon is the picture of its creator: an abomination with three writhing tails, monstrous wings, and two hideous heads. Initially, each bulbous head appears featureless—a disturbing, preternatural bud yet to bloom. When threatened, however, each unfurls to reveal a flower-like arrangement of glistening flesh and teeth around two crushing jaws.
Though the head of the dragon from which the demodragon spawned is long gone, its breath remains. Without warning, the demodragon can unleash a deluge of bone-melting acid on any who dare challenge it.