Muck Valley Cavern is a small, one zone, cave that contains Sibylla Draconis and her different types of animals. The cave is located due east of the Shrine of Vaermina. The cave is a part of the Dark Brotherhood quest "Next of Kin".
The first opening contains a Rat and a Wolf, the second opening contains three Rats and finally the third opening contains two Rats and Sibylla Draconis. At higher levels, the first opening will contain a Rat and a Mountain Lion, and the second containing a Brown Bear and a Black Bear.
The sacks next to the table and the fire contain three/four vegetables.