Cerberus

In Greek myth Cerberus was a horrific dog who stood watch at the gates of Hades, the world of the dead. Cerberus had three heads (some accounts gave him many more) and was so vicious that he was feared even by the gods. Cerberus is most famous for his role as one of the 12 labors of Hercules, the strong man who ventured to Hades and wrestled Cerberus into submission. Cerberus also appears in the story of Orpheus, who lulled the dog to sleep with music on his way into Hades to search for his lover Eurydice.