A Deep Dwarven community. Home of many Dwarf Battle Ragers. Mentioned in the background of Sturm Gerwycht.
There's a Dwarven kingdom (or set of kingdoms, perhaps) called Thrusch somewhere in the world, according to my dear old Sturm's background. Probably in mountains, but not necessarily -- could be a network of caves accessible through a canyon, or something of that sort. It goes deep, though -- Down Thrusch is Sturm's home, and it's pretty much in / right on top of whatever layer would be analogous to the Underdark (although the closest personal threats are kobolds, it's kind of built into their culture that they have to chase out much nastier things from time to time.)