In Greek mythology, the god of the underworld known for his three-headed dog is Hades. Cerberus, the three-headed dog, guards the gates of the underworld, preventing the dead from escaping. Hades is often misunderstood, as he is not inherently evil; rather, he governs the realm of the dead, ensuring it remains a place of order. His figure emphasizes the inevitability of death and the respect due to those who have passed.