Lieutenant of the Tower of Barad-dûr

From Tolkien Gateway
The Lieutenant of The Black Tower of Barad-dûr by John Howe

Lieutenant of the Tower of Barad-dûr was the title of an important commander in the land of Mordor. Its associated details and duties are unknown, but at the time of the War of the Ring it was borne by the Man known as the The Mouth of Sauron.