The cave system branches and winds throughout the mountain. if you go down far enough, and know the way, you reach a cavern that catches enough sunlight that its walls have turned all to the yellow stone. In its floor is a crack that you can look through to see the ocean far, far below.
There is nothing, in all the caves, that seems like it needs guarding; but if you listen closely you can sometimes hear echoing voices in the distance, and grinding stone. If you make your way to where you think the sounds came from, you find only the empty tunnels.