The Chimera is an amalgam of multiple creatures, it has two heads, a pair of colossal wings and a tail equipped with a serpent's head. It is known to rely on teamwork between it's two heads, one of the heads throws the fuel, and the other head generates a super heated breath which ignites in mid-air.
The Chimera are supporting antagonists in the film.
The Chimera is among the plethora of creatures unleashed by Hades into the Earth. A horde of Chimeras is unleashed near Perseus' village, and at least one of them targets Perseus' village and wreaks havoc killing and burning whoever comes on it's way, however Perseus arms himself and manage to slay the Chimera by tricking one of the Chimera's head to spew fire while the second head was injured and bleeding a flammable liquid, thus causing the Chimera to burn itself.