Zaulfung
Zaulfung, the "Devil Swamp", is vast region to the east of Riverhaven thought to be a creation of The Waste. It was home to the graceful palace of Empress Merthamone prior to 400 BV. Today it's a swamp tainted by a malign land-devouring spirit held at bay by magic, haunted by the dead, and infested with dangerous beasts.
The demon gained foothold in our plane due to a weakening of interplanar barriers, subsequently laying waste to the land as it created a permanent home for itself. The corruption was confined by the Zaulfung Stones which reinforce the interplanar barrier, preventing further ruptures. The creature was known as the "Nameless Evil of Zaulfung" for decades until its power rose once again and it revealed itself as the demigoddess Maelshyve.
Amidst the prevalent death and decay, the chimera-shaped temple Kweld Gelvdael stands as a sacred guardian against the horrors lurking far beneath the marsh.