The Greek Underworld is a mythical realm ruled by the god HADES. It is also known as the House of HADES or the Realm of the Dead. HADES is the god of the dead and the ruler of the Underworld. He is often depicted as a dark figure with a helmet and a three-headed dog. The Underworld is a place of punishment for those who have committed crimes in life, and it is also the final resting place for the souls of the dead.