Gumar is a valley between the Netheram mountain range. It is a dark desolate place that gets no rainfall. It is shadowy and dark from the floating island above it. In the Lith-Crillion Era, Krarkauk stopped over this valley. It has not moved since that time.
Gunmar is a haven for things of the night. There have been colonies of drow and illithids that built settlements in this area. These groups are cleaned out periodically by the cloud and storm giants that live on Krarkauk. The area is also the abode of shadows, vampires, and other undead which have a particular affinity for dark and shadowy areas. Due to the threat of the unknown from Gumar, Netheram's frost giants and other humanoids have learned to build fortifications with layers of defense and using all manner of light producing things. These places are constantly bathed in the glow of great braziers of burning oil, torches, and magical light.