During the Planar Wars, Mezulbryst inadvertently became merged with parts of the Abyss, rearranging its geography. Little is known about its pre-corrupted layout, although the city of Stygia predates the merger.
A large mountain range lies to the south of the Stygian Sea.
The River Styx flows north from the mountains, past Iron City and Stygia, and empties into the Stygian Sea. The River Acheron flows south, past Shieltas and through drow territory. The cities of Ameliel and Asinos lie to the west of the River Acheron, and South Toven lies to the east. The River Lethe flows through territory occupied by humans, the most lush area of Mezulbryst, past the city of Schade and into the Stygian Sea.
The River Cocytus runs down from the frozen northern mountains into the north coast of the Stygian Sea.
The Abyss formerly had an opening near Shieltas, and the demons there terrorized the drow living in the area. Riven Soulfire fought against the demons, and eventually prayed to Keolah, who swept the demons away and moved the entrance to the Abyss away from Mezulbryst entirely.
Riven's actions in the Demon Wars propelled him to the top of the drow army. Another war was fought against the human dreamwalker, Nero, who led the armies of Schade against the drow. With the aid of drow from Wilderplane, Riven secured victory against Schade.