Stygia

Stygia, also known as Hades, Dis, and Erebos, is the Underworld of the Olympian Pantheon. The souls of all mortals claimed by the Olympians venture here, where they will be judged based on the deeds they committed in life, and then be consigned to whatever region of Stygia that their living actions earn them.

Stygia is ruled by Hades, and his queen, Persephone. Other notable residents include Thantos, the Olympian God of Death, Hecate, the Goddess of Magic, and Charon, the ferryman who takes the dead across the River Styx.

Geography
Stygia appears to be an utterly gargantuan subterranean cavern, with a rocky ceiling that stretches as high as the sky, which is often obscured by puffs of smokey clouds. It is possessed of numerous mountain ranges, ashen deserts, forests, fields, and even oceans.

The River Styx
The River Styx is the most prominent river within Stygia, and is the source of the realm's name.