What is the Underdark? In Forgotten Realms, the Underdark is the series of caverns and caves that house the (mostly evil) races that live underground. While I like the idea of an Underdark for Arenthyor, the name "Underdark" has always struck me as being Surface-centric. I mean that a drow, for example, who has lived her entire life in the lightless depths and the comforting enclosures would not consider herself, her world, to be "Under", nor "dark", for those are concepts that would be foreign to her. She would consider her world to be the center of the universe, not below something that she has never experienced (the surface world) nor would she comprehend the world of light in order to recognize that she lives in darkness.