Starless Lake
The Starless Lake is a huge body of water in the Underdark. It is fed in part by the Murghom River and in part by the collected foul waters that drain out of the Mountains of Copper. It is said that if you dip a hand into the lake it will form a rock hard crust in a short time.
The lake takes several hours to cross if you know where you are going, and longer if you do not know the pathways across. There is a tribe of mongrel men who have made a business of selling boats to travelers to cross the eastern part of lake. Those who need to cross can purchase a boat on one shore and are given directions to the next set of docks. The boats can then be resold at that dock to recoup part of the passage fees. There are a total of 4 docks that stretch from the far northern shore of the lake and are spread out on the eastern side of the immense cavern that the lake fills to the far south. The southern docks are only a couple hours march north from Khazefryn.
Travel from the southern docks near Khazefryn to the northern docks is against the current. There are two rivers that flow out of the Mountains of Copper and into the lake that create openings that need to be crossed before reaching the next set of docks. That set of docks is where the Deep Dark Dangerous path that leads to Morten meets the lake. If a traveler continues north along the lake's shore the next set of docks intersects with the Long Winding path that leads to the mines near Morten. The far northern docks lead to passages that go even farther and deeper into the Underdark as they wind towards the Great Mountains.