The Star Stone is like the Moon pool and the moon stone in warriors. It is located on the edge of Sootclan territory, right beside the forever meadow. (Basically in between Sootclan and Rainclan)
Leaders can come here to receive lives and Medicine cats come here for meetings or just to get closer to Starclan.
A lucky apprentice such as the leaders apprentice or deputies apprentice may get to visit here at some point throughout their apprenticeship.