Nithrau

Nithrau was the Elvish name for all the land under the surface of the island of Enniare, also known as the Shadow Lands. It was an enormous underground cavern about as geographically large as the entire island of Enniare, as well as directly beneith it. It was located directly above the subterrain Gnomish nation of the Underlands. Most of the floor of Shadow Lands was covered by an underground lake called the Sea of Darkness. At the southern end, the waters were shallow enough to wade in. At the North end of the cavern, the lake ended and a jagged mountain rose up into the cave, whereupon the Dasu'r erected their Dark Castle and established dominance over the earthmen living there.