Stygia is a fictional land in the Dungeons & Dragons universe, often depicted as a dark and foreboding realm. It is part of the Outer Planes and is associated with the River Styx, a mythical river that souls must cross to reach the afterlife. Stygia is characterized by its icy landscapes and is inhabited by various creatures, including demons and undead beings. In many stories, Stygia serves as a place of punishment and despair, reflecting the consequences of evil deeds. The realm is ruled by powerful entities, such as Set, a serpent god, who embodies treachery and darkness. Adventurers may find themselves navigating its treacherous waters and facing formidable foes.