"The Crystalmir Lake, that's what the first adventurers named this place for the way torches reflected off the water. Rumor has it, people used to visit the dwarves here to learn about their secrets of knowledge through trade. It helped make this area safe, a lost feature now that the kobolds and troglodytes have overrun the place. When I first visited this place, I found old notes scattered around detailing a failed meeting between us humans and the dwarves. It sounded like the dwarves never showed. We tried exploring the caves further in to learn more information, but that was a mistake - It was a slaughter. Most of my men were nearly killed. The only reason I'm alive to write this journal is because I hid behind a rock while my guard was dragged into the lake. I don't think I will return to the Underdark."
Ahnir Namer, Journalist and Scholar
is fortunate for having a fresh source of water; the lake obtaining the water from the dripping ceilings above. The official measurement has not been recorded, but the humans and dwarves agreed that the length and width has to be several miles. At least, it would be far too dangerous for any living creature to swim from one edge to the other. For those interested in depth, the murky waters would make it impossible to determine.
This lake is also one of the few regions within Athelney
to have an abundance of space for larger creatures. In terms of distance to the surface, it could be noted that it's safe enough for the humans to make frequent trips here. For how long it takes to reach the surface is unknown, as time is still impossible to comprehend in the Underdark.
Excluding fresh water from the Crystalmir Lake, the region still provides valuable resources with sunken mineral rocks in the water. This is also one of the preferred places to grow vital components for making potions, which is one of the things dwarves used to exploit. The ability to farm here comes from the fresh water and damp conditions that various mushrooms require.
Flora & Fauna
Strange living orgasms are known to survive in the Crystalmir Lake: the most famous are the large crabs around the size of domesticated dogs. It's ill-advised to swim, yet people frequently use this location to fish for food.
Fortunately for those who rely on light sources, the walls have been riddled with soft green mold that produces a soft light glow. This light seems to reflect off the walls and water to illuminate the outline of the lake. The humans have clearly documented hazardous results for those who attempt to eat the mold.