Towers of the Teeth
At the northwest corner of Mordor, the Ephel Dúath and the Ered Lithui came together at the haunted Pass of Cirith Gorgor, and formed a gateway into that dark land. In the early days of Gondor, after Sauron's first defeat, the Gondorians built two watchtowers at the entrance to the pass, to guard Mordor and prevent the return of Sauron's servants. They failed, and the watchtowers fell under the control of the Red Eye. They became known as Carchost and Narchost, the Towers of the Teeth.
Other names include the Teeth of Mordor, the Towers of the Black Gate, and the Watch-towers of Morannon.