The Underdark

The Underdark refers to the vast underground cave network in the depths of the Prime Material Plane. Locations can be found almost anywhere underneath landmasses, ranging from hundreds of feet below the surface to hundreds of miles below. It has its own sustaining ecosystem, featuring creatures such as myconid, basilisks, duergar, mind flayers, and many more. Notably, the Underdark was the home of the Drow during the Age of Elves.