In Greek mythology, Cerberus was the three-headed hound guarding the entrance to the Underworld.
Cerberus was usually described as the offspring of Typhon and Echidna, two monstrous figures in Greek mythology. His siblings included Orthrus, a two-headed dog, as well as the Hydra and the Chimera in several ancient traditions. Cerberus’s multiple heads allowed him to watch the realm of the dead from different directions.
The dog’s main task was to prevent the dead from escaping and the living from entering without permission. Despite his fearsome reputation, Cerberus was overcome by Heracles during the hero’s final labor. Heracles brought him to the surface as proof of completing the task, then returned him to the Underworld.
Ancient sources do not always agree on Cerberus’s exact appearance. Some accounts give him three heads, while others add a serpent for a tail, snakes around his neck, or many snake heads along his back. He is often confused with Orthrus, another monstrous dog associated with Geryon.