The "Three-Headed Dog," known as Cerberus in Greek mythology, is a monstrous creature that guards the entrance to the Underworld. It is typically depicted with three heads, a serpent for a tail, and a mane of snakes. Cerberus prevents the dead from escaping and the living from entering without permission. In art and literature, Cerberus symbolizes the boundary between life and death. The creature is often associated with Hades, the god of the Underworld, and appears in various myths, including the famous tale of Heracles, who was tasked with capturing Cerberus as one of his twelve labors.