The Underdark

The Underdark is a vast network of caves deep underneath Ortheid. Until a tunnel was found beneath Vol Thorim, The Underdark was assumed to be a Dwarven folk tale.

The Underdark is home to the Duergar, a close relation of Dwarfs that have greyish-blue skin, and generally quite bright hair. According to the Dwarven folk-tales, the Duergar were originally a tribe of Dwarfs who became addicted to the pursuit of treasures. After digging far too deep and discovering the Underdark, this tribe got lost, eventually making a deal with The Elder Brain to stay alive.

According to other folk-tales, The Underdark is also home to The Illithids, a horrifying humanoid race of creatures that are said to be able to read the darkest secrets of those that enter their lair.