Yrngreirn is a very deep lake in a cooler part of Borngring's highly geothermal landscape. It has a shoreline riddled with geysers, a playground for steam mephits, water weirds, and water elementals. Considered pranksters, robbers and troublemakers, the steam mephits are not all bad. Along the northern shore are the Great Bathhouses of Yrngreirn. Steam mephits have been running these steam bathhouses since the God Era.
The area is often foggy, visibility mere feet or less. The surface of the lake is often covered with algae and discolored from minerals and toxins. The algae is something of an aphrodisiac to the aboleth. In the Horgon Era, the Hofthorm Monarchy (145 HE - 101) controlled this area, selling buckets of the stuff to eager buyers destined for the sunken fortress of Halanneg. Today, the aboleth of this place, ancient creatures beyond measure, still collect Yrngreirn's algae; what they call Yrngreirns Serum, the only thing from keeping them from becoming sterile.
On the lake's eastern side, towards the city of Harknori, are fishing villages populated mainly by fire giants, orcs, and Corralum and Minâth ex-pats of the Khazarkar Empire. Most of these villagers are citizens of the Gangvori Syndicate.
Yrngreirn descends into Riwthor, a subterranean sector of the Faeglor Region. In this area, taps into the lake's lowest depths serve as faucets for drinking water, collected and sold by the aboleth lords of Halanneg. Most of this lake water is destined for the extremely dry caverns surrounding Moltaria.