Coalfens
The Coalfens are a large swamp region south of Vesuva containing a singular "mountain" which is really a large hilltop feature, with a deep cave inside called The Hall of the Great Wyrm, in which may be found a Portal which was built during the Ulon-Zirak as a tactical defense point. Since that time, the remains of the Battle of Karthus Vale during the War on the Under-Dark festered and fell to darkness and ruin, the assumed final resting place of the ancient Black Dragon, Ïátu, living his wounded and cursed existence, and pouring his hatred and his malice into the swamp.