Greek Mythology/Beasts/Cerberus

Cerberus, (In Greek: Κέρβερος), was a three-headed or hundred-headed dog that guarded the gate to the underworld of Hades, where the dead went to rest. Cerberus was always vigilant; the heads would alternate resting and guarding, thus ensuring constant vigil. Cerberus was overpowered and carried off by Heracles as one of his tasks for the King of Mycenae. The musician Orpheus also overcame Cerberus by lulling him to sleep by playing the lyre, in order to bring his beloved back from Hades.