The Two Watchers were two carved figures that guarded the arched gateway through the outer wall that led to the courtyard of the Tower of Cirith Ungol.
Description
The Two Watchers were great two figures that were sitting on thrones on both sides of the gateway. Their figures were formed of three bodies with heads with the faces of vultures with eyes of black stone. One head looked outward, one head looked inward and the third head stared across the gateway itself. They were inhabited by "some dreadful spirit of evil vigilance". Not a visible or invisible creature was unnoticed by them. They had the power to identify enemies and to block them from entering or from exiting through the gate with the force of their will alone, and were able to send up a shrill alarm call if their guard was breached.
It is possible that the Two Watchers were not created by the Men of Gondor, because a "dreadful spirit of evil vigilance" existed in them, they perceived a Hobbit as an enemy and made a high shrill cry when he passed them, but let Orcs pass the gateway without making such a cry.
On 14 March T.A. 3019, the Two Watchers blocked Sam's initial attempt to pass through the gate. However, Sam was able to overcome the will of the Two Watchers with the help of the Phial of Galadriel and was able to pass through the gate into the court of the Tower of Cirith Ungol in a second attempt. When he passed the gate, the Two Watchers uttered a high shrill cry, which was answered by a single clang of a bell high up in The Tower of Cirith Ungol. After hearing the bell the orc Snaga said to the orc Shagrat that a great fighter, an Elf or a Man of Gondor ("tark") got past the Watchers, and that's tark's work. It is probable that he meant that the feat of getting past the Watchers was the work of a Man of Gondor.
Later that day, in order to leave the Tower, Frodo and Sam held up again the Phial while invoking Eärendil and Elbereth, which broke the will of the Two Watchers so that they were able to pass through the gate to the outside. The keystone of the arch and the wall above the gate crumbled into ruin after they passed, but the Two Watchers uttered a high and dreadful wail.