Underdark

The Underdark is the subterranean setting of Dungeons & Dragons campaigns and fiction. In Baldur's Gate 3 it is a large underground area accessible through multiple locations, each entrance leading to a different environment; act one ends when the party crosses the mountain pass or the Underdark to reach the setting of act two, and the party travels through the mountains or the Underdark to reach Moonrise Towers. Faerun's Underdark holds drow cities such as Menzoberranzan and the ruins of Ched Nasad, and duergar cities such as Gracklstugh and Dunnspeirr.