Grasp of Orcus
Though its name might evoke images of a single subterranean body of water, the Darklake is a network of underground rivers, natural tunnels, and canals that connect innumerable water-filled caverns and chambers. This vast waterway stretches over a hundred miles across, with ceilings that are miles high in some places and depths that are unfathomable.
Long ago, duergar engineers extended and widened many of the interconnecting passages of the Darklake. They also constructed locks for raising and lowering watercraft to different levels within it, opening up large portions of the network for travel. Many Underdark creatures are experienced in navigating the Darklake, including the kuo-toa – fishlike humanoids known for their insane obsession with unraveling the secret patterns of the Underdark. Still, better to trust a kuo-toa guide than attempt to traverse the Darklake alone and become lost within it forever.