Three Erebon Shrines generate in the Ancient Cavern. Two generate in the main room, and one generates within Penumbra's chamber.
The Erebon Shrine has two functions based on its position within the Ancient Cavern. If used outside of the Ancient Cavern, the Erebon Shrine does nothing.
When interacted with, the Erebon Shrine in Penumbra's chamber will teleport the player back to the main room. This will also remove 20 Erebon tribute points from the player.