Cerberus or Kerberos, in Greek and Roman mythology, is a multi-headed (usually three-headed) dog, or "hellhound" with a serpent's tail, a mane of snakes, and a lion's claws. He guards the entrance of the underworld to prevent the dead from escaping and the living from entering. Cerberus is featured in many works of ancient Greek and Roman literature and in works of both ancient and modern art and architecture, although the depiction of Cerberus differs across various renditions. The most notable difference is the number of his heads: Most sources describe or depict three heads; others show Cerberus with two or even just one; a smaller number of sources show a variable number, sometimes as many as 50 or even 100.
The jaws are hinged and removable, and the collars have actual chains.