Pluto's Realm is a term used to refer to the underworld in Greek mythology, ruled by the god HADES. It is also known as the Lowerworld, and is often referred to by its five-letter name, HADES. The realm of Pluto's is a dark and gloomy place, where the souls of the dead are said to reside. It is a place of punishment for those who have committed wrongdoings in life, and is guarded by Cerberus, the three-headed dog.