Moss Rock Cavern is a cave north of the Imperial City and just north of Roxey Inn. It is a dark, natural cavern that is rife with coffins with two dark altars and a small shrine that appears dedicated to Molag Bal and Namira. There are a small number of Cairn Bolete mushrooms inside.
The cave is inhabited by Raelynn the Gravefinder, her fellow Necromancers and associated undead. The Hero is sent here by Malene at the Roxey Inn as she claims the Undead often wander outside at night.
Roxey Inn is in the wilderness north of the Imperial City. The owner there, Malene, asks the Hero to help her rid the area of a Necromancer who calls herself Raelynn the Gravefinder. She can be found in Moss Rock Cavern to the north.