Rannveigs Fasten is a Nordic Ruin located just south of Morthal. It is the hiding place of Sild der Hexenmeister who has killed a number of people and subjugated their ghosts, using them as guards. When they attack, these ghosts all say "I'm sorry, this isn't what I want".
At the back of the main chamber is a conspicuous chest. The unwary will likely fall down the trap door directly in front of it, landing in a locked, semi-submerged cage with a number of dead bodies. This cage is in Sild's lab.
In the lab is a table with an Alchemielabor, an Ungewöhnlicher Stein, a copy of Das Grauen auf Burg Xyr and Silds Tagebuch. There are also a number of cells, some with victims still in them, albeit dead ones.