Muil was the westernmost of the Seven Isles and was one of only two known to be documented.
The Seven Isles were frequently visited in the Golden Age of Narnia. However, during the Age of the Telmarines, they, like all Narnian sea colonies, were neglected. Muil had a population in the time of Caspian X, and was visited by him during his epic voyage into the Great Eastern Ocean. When rumours of Aslan were heard in the islands, Caspian X set sail once more to visit the Seven Isles.