The Underdark is a vast subterranean realm that has been featured in various Dungeons & Dragons campaign settings and novella. This realm consists of a seemingly infinite network of tunnels and caverns that run beneath the surface world, spanning across and between entire continents. Its environment is hostile and uninviting to surface-dwellers, and only the bravest or most foolhardy of adventurers dare to travel its bleak depths.
There is no complete map of the entire Underdark and it has no centralised government; it is divided into various city-states which each have their own style of governance. The inhabitants of the Underdark are primarily evil-aligned or simply incapable of surviving on the surface due to an intolerance for sunlight.
Below is a list of creatures known to dwell within the Underdark.