The Underdark

Extending miles downward and outward beneath the surface of Faerûn, and reaching to other continents as well, the great network of subterranean caverns known as the Underdark is home to all manner of strange and deadly creatures. Duergar and drow—dark reflections of dwarves and elves—live in these sunless lands, as do the svirfneblin, or deep gnomes. Most surface-dwelling folk aren't threatened or even disturbed by denizens of the deep places, but the creatures occasionally emerge to raid or to seek some kind of goal in the surface world.

Among the lands of the Underdark beneath the North are the svirfneblin city of Blingdenstone, the duergar city of Gracklstugh, and the infamous drow city of Menzoberranzan. Also prominent is Mantol-Derith, a trading post for Underdark merchants.