Orthrus

A two-headed Orthrus, with snake tail, lying wounded at the feet of Heracles (left) and the three-bodied Geryon (right). Detail from a red-figure kylix by Euphronios, 550–500 BC, Staatliche Antikensammlungen (Munich 2620).

In Greek mythology, Orthrus (Ancient Greek: Ὄρθρος, Orthros) or Orthus (Ancient Greek: Ὄρθος, Orthos) was, according to the mythographer Apollodorus, a two-headed dog who guarded Geryon's cattle and was killed by Heracles. He was the offspring of the monsters Echidna and Typhon, and the brother of Cerberus, who was also a multi-headed guard dog.