In Greek mythology, Cerberus represents the three-headed dog that guards the entrance to the underworld. It had three heads, a dragon's tail and snakes instead of hair on its head. Cerberus was the son of the giant Typhon and Echinda.
Cerberus came out of the underworld only once, and that was when Heracles led him out. For he was given a task by the Mycenaean king Eurystheus to bring him Cerberus. With the help of the gods, Herakl─ôs made it to the underworld, where he was welcomed by Hades himself. He allowed him to capture Kerber, but only with his bare hands. But Herakl├ęs managed it and led Kerber to Mycenae. As soon as Eurystheus saw the terrible creature, he fell to his knees and begged that Cerberus be taken back.
Cerberus had several siblings, who were Orthos (a two-headed dog), Chimera (a monster with the body of a lion, the middle of a goat and the back of a dragon, which breathed fire with three mouths), Sphinx (a monster with the head and chest of a naked woman, the body of a lion, the tail of a snake and the wings of an eagle) and Hydra (a monster with the body of a snake and nine dragon heads).