Moondeep Sea

The Moondeep Sea was a subterranean lake, approximately wide, found in the Underdark beneath the Galena Mountains and the cold plains of Vaasa.

Geography
The cavern which contained it was known as the Vault of Gnashing Teeth, so named for the countless animated skulls stuck to the cavern's ceiling. The water of the lake was fed from the Great Glacier.

The Moondeep Sea was known for its giant water spiders and the city of V'elddrinnsshar‎, which lay on a mile-wide island dominated by a plateau in the middle of the lake.