The Watchers of Cirith Ungol were two statues guarding the entrance to the Tower. They were formidable black statues with three joined bodies, three vulture-like faces, and clawed hands. The orcs of the Tower mention them being “tark’s work”, which references the Numenoreans, as Cirith Ungol was built by them in the beginning of the Third Age but lost to Sauron. During the time of the Quest of the Ring they are known to contain an evil spirit. Gandalf warns the Fellowship of them as the “Silent Watchers” as they plan their infiltration of Mordor. They functioned as both sentry and alarm system for any intruders. Samwise encountered the Watchers during his mission to save Frodo after his capture. He could not bypass the Watchers as they created an invisible obstacle with strength compared to Shelob’s web. He used the Phial of Galadriel to break through the barrier. As he passed the Watchers, they let out a shrill cry, a warning to the denizens of Mordor and the orcs of the Tower. Samwise saved Frodo, feeling the Watcher’s dread until the escape where he had to fight the Watchers’ barrier once more. He used the Phial, but this time Frodo and Sam conjured some Elvish magic to break through. As they fled, the Watchers’ shrieked for the last time, and the gateway came crashing down. Better than a “Beware of Dog” sign.
“They were like great figures seated upon thrones. Each had three joined bodies, and three heads facing outward, and inward, and across the gateway. The heads had vulture-faces, and on their great knees were laid clawlike hands. They seemed to be carved out of huge blocks of stone, immovable, and yet they were aware: some dreadful spirit of evil vigilance abode in them. They knew an enemy. Visible or invisible none could pass unheeded. They would forbid his entry, or his escape. Hardening his will Sam thrust forward once again, and halted with a jerk, staggering as if from a blow upon his breast and head. Then greatly daring, because he could think of nothing else to do, answering a sudden thought that came to him, he drew slowly out the phial of Galadriel and held it up. Its white light quickened swiftly, and the shadows under the dark arch fled. The monstrous Watchers sat there cold and still, revealed in all their hideous shape. For a moment Sam caught a glitter in the black stones of their eyes, the very malice of which made him quail; but slowly he felt their will waver and crumble into fear.“ – Samwise coming face to face with the Two Watchers. Return of the King, The Tower of Cirith Ungol.