Cerberus

Cerberus was the fearsome guardian of the underworld in Greek mythology, a monstrous multi-headed dog who prevented the souls of the dead from escaping Hades' realm. Born to the monsters Echidna and Typhon, Cerberus was typically depicted with three heads, a tail made of a living serpent, and snakes emerging from various parts of his body.

The creature is most famous for his role in the twelve labors of Heracles, where capturing the mighty hound of Hades alive was the hero's final and perhaps most dangerous task.