Hydra

The Hydra had the body of a serpent and many heads (the number of heads deviates from five up to one hundred there are many versions but generally nine is accepted as standard), of which one could never be harmed by any weapon, and if any of the other heads were severed another would grow in its place (in some versions two would grow). Also the stench from the Hydra's breath was enough to kill man or beast (in other versions it was a deadly venom). When it emerged from the swamp it would attack herds of cattle and local villagers, devouring them with its numerous heads. It totally terrorized the vicinity for many years.