Orthrus

Orthrus is a demon in the series.

Orthrus was a two-headed dog and one of the many monsters sired by Typhon and Echidna from Greek mythology. Among his siblings were Cerberus, Sphinx and Chimera to name but a few. Orthrus was the dog of the Titan Geryon, and along with Eurytion, was the guardian of Geryon's herd of red cattle. Geryon, Eurytion and Orthrus were all slain when Heracles was completing the tenth of his twelve labors.