Cerberus

 Cerberus  is a mythical 3-headed hound said to guard the gates of Hades in Greco-Roman literature and mythology, never allowing the escape of a person who has already crossed the River Styx. Cerberus was generally believed to be siblings with the Chimaera, Lernaean Hydra , Sphinx , and Nemean Lion; and the child of echidna and Typhon. One of the Labors of Hercules was to capture Cerberus, and Hercules was able to not only overpower the dog without weapons, but also used it as leverage with King Eurystheus to end the Labors. When Orpheus went to the underworld to retrieve his wife he is said to have put him to sleep by playing music on his lyre. In Dante's The Inferno,

cerberus  Cerberus guards the third circle of hell, the Gluttons, ripping apart those who reside there.