Cerberus

Cerberus is the watchdog of the realm of Hades, generally described as being a three-headed dog with a serpent tail, and on his back innumerable snakes' heads. He is believed to be the son of Echidna and Typhon, brother of Orthrus, the monstrous dog of Geryon, of the Hydra of Lerna, and of the Nemean lion. Chained in front of the gates of the Underworld, he terrorizes souls upon their entering. Cerberus was bested by men such as Heracles and Orpheus. He stops barking if you throw him some bread soaked in wine. "To give a sop to Cerberus" means to present someone who is likely to cause trouble with a gift in order to keep him quiet, but this works best on dogs.