Drenka Cavern is a large cave in the Boethiah's Spine that leads to a daedric shrine. The cave is tucked away in the Boethiah's Spine and can be tricky to find. From Tel Oren, head over the bridge and keep heading in the same direction until you pass under a rock arch. On your right, before you reach the Veramus Iron Mine, there is a set of stone steps. Climb these and follow the path around to the south: the cave lies at the end of the tiny valley.
There's little of interest in the cave itself: two bottles of Shein stand on a crate of iron armor, and a crate of kwama eggs stands nearby, but that's it. Ten leveled creatures and three daedric bats guard the cave, along with the thief Naruni Drethan, who can't be very good if this is all he has managed to steal. Perhaps more interesting is the entrance to the Daedric Shrine of Lambinatha at the southeastern end of the cave.