The symbol for Hades is his helmet, also know as the helm of darkness. He is also known by his guardian, which was a three-headed... The symbol for Hades is his helmet, also know as the helm of darkness. He is also known by his guardian, which was a three-headed dog. Hades, son of Cronus and Rhea, was the God of the Underworld. It was believed that he ruled the Underworld and this led to the word Hades becoming synonymous with death. Hades rarely left the underworld and he had a guardian named Cerebus. This three-headed dog protected the realm by keeping out those who did not belong there.