A swampy region along the Sword Coast North that sits in between Leilon and Waterdeep, the name is in reference to the thousands of dwarves, elves, and humans of the Fallen Kingdoms who were slain during the invasion of the undead and mercenary armies centuries back.

It is a desolate place full of monsters and few members of the civilized races. The swamp constantly grew over time, swallowing homes and property located close to its boundaries, causing many to believe that the eastern boundary of the Mere was magically bound to the High Road since attempts to reroute the road were futile and only caused the expansion of the swamp.

The Mere itself is full of trees, vines, quicksand, and hidden islands, and it was generally covered in fog, making visibility very poor. The bones of fallen creatures are clearly viewable throughout the Mere, the water was so shallow that it could only be navigated on a flat-bottomed boat, with the dark water and hidden obstructions making that choice dangerous.

Inside the Mere were the flooded ruins of a number of castles and settlements. Many of the castles had strange wards that would either strengthen certain magic or negate it.