Cerberus is descended from Typhon, creator of storms, and the serpent goddess Echidna, daughter of Callirrhoe and Chrysaor, a giant who was son of Poseidon and Medusa. The children of Typhon and Echidna were a mixture of creatures similar to animals (legend says this was due to a curse sent by a goddess). Cerberus soon was left by his parents; Typhon was imprisoned in Mount Aetna after his insolvent rebellion against the Olympians, and Echidna marched to Libya, where she kidnapped children to feed to Cerberus and his brothers. Finally, she was assassinated by Argus, a giant. Cerberus was later used, by Pluto, God of the netherworld, to maintain order in his kingdom after the Titans were defeated. Cerberus assassinated Keres, an old spirit who punished and terrified the dead, and later occupied its place at the doors of Hades, taking on his mission: to prevent those who entered from leaving, and send the living back to the world above.
Few have managed to leave Hades without the permission of Cerberus; among them is Orpheus - son of the muse Caliope - who, after returning from his adventures with the Argonauts, discovered that his beloved Eurydice was dead, and went to Hades to rescue her. He confronted Cerberus, but, with his music, Orpheus mesmerized the guardian of Hades, and gained access to the netherworld. The mortals Theseus and Peirithous managed to distract to Cerberus sufficiently to enter Hades, to try to abduct Persephone. Perhaps finally, there was the remarkable feat by which Hercules was able to, in the last of his mythical Labors, capture Cerberus, and take him to the court of the Mycenaens, and Eurystheus.