The court of the earth spirits beneath the mountains west of the Empire, ruled by The Earthen Queen. Its guards are man-shaped boulders that come out of the rock face and move through solid stone as though it were water; being carried through it takes several minutes and is not survivable by anyone the Court does not intend to arrive.
Everything in those mountains is its realm, whether or not a human knows it. A cave offered to somebody else, by somebody who never asked, is still theirs. You should have been aware, human. Everything is someone's realm.