The Dead Men and Aragorn
The Dead Men of Dunharrow, also called the Oathbreakers, the Grey Host, the Shadow Host, or the Sleepless Dead, are the spirits of a people who dwelt in the White Mountains during the Dark Years. In the beginning of the realm of Gondor, their king swore allegiance to Isildur upon the Stone of Erech, a black stone brought from Númenor. But when Sauron returned and grew in might, Isildur summoned the Men of the Mountains to fulfil their oath and fight against the Dark Lord. They refused, for they had worshipped Sauron in the Dark Years. Isildur then laid a curse upon them: they should rest never until their oath was fulfilled. They fled before his wrath, hid in secret places in the mountains, and slowly dwindled, becoming a terror to the living. The fear of the Sleepless Dead lay about the Hill of Erech and all places where that people lingered.
The Summoning at the Stone of Erech
Aragorn, the Heir of Isildur, took the Paths of the Dead at the urging of Elrond's sons, Elladan and Elrohir, who brought word from their father: "The days are short. If thou art in haste, remember the Paths of the Dead." Aragorn led the Grey Company—the Dúnedain of the North, Legolas, Gimli, and the sons of Elrond—through the Dark Door under the Dwimorberg, the Haunted Mountain. The horses refused the way, and Gimli, though a dwarf accustomed to deep places, was struck blind with fear, hearing the whisper of countless voices and feeling an unseen host following in the dark. At the Stone of Erech, Aragorn blew a silver horn and cried aloud: "Oathbreakers, why have ye come?" A voice answered from the night: "To fulfil our oath and have peace." Aragorn declared himself Elessar, Isildur's heir of Gondor, and commanded them to follow him to Pelargir upon Anduin, promising that when all the land was clean of the servants of Sauron, the oath would be fulfilled and they would depart for ever.
The Ride to Pelargir
The Grey Company rode with the Shadow Host behind them, a great army of invisible shapes that spread terror before them. They passed through Lamedon, where the folk fled at the rumour of the King of the Dead. They crossed the Ciril and the Ringló, and came to Linhir above the mouth of the Gilrain. There men of Lamedon were fighting the Corsairs of Umbar and the Haradrim, but both defenders and foes fled when the Grey Host appeared, crying out that the King of the Dead was upon them. Only Angbor, Lord of Lamedon, had the courage to abide them. Aragorn bade him gather his folk and follow behind. At Pelargir, the main fleet of Umbar lay at anchor. The Haradrim, driven to the brink, turned at bay, fierce in despair. Aragorn halted and cried: "Now come! By the Black Stone I call you!" The Shadow Host swept forward like a grey tide, and none could withstand them. The Dead passed over the water to the anchored ships, filling the mariners with a madness of terror so that they leaped overboard. The captives chained to the oars were freed. By the end of that dark day, no enemy remained to resist the Heir of Isildur.
The Release from the Curse
Aragorn chose the greatest ship for his own and let sound a great concourse of trumpets taken from the enemy. The Shadow Host withdrew to the shore, standing silent, hardly to be seen save for a red gleam in their eyes. Aragorn spoke in a loud voice: "Hear now the words of the Heir of Isildur! Your oath is fulfilled. Go back and trouble not the valleys ever again! Depart and be at rest!" The King of the Dead stood out before the host, broke his spear, and cast it down. He bowed low and turned away, and swiftly the whole grey host drew off and vanished like a mist driven back by a sudden wind. Legolas, who had felt no fear of the shadows of Men, said that it seemed to him as if he awoke from a dream. The Dead Men were gone, their ancient curse lifted at last by the coming of the rightful king.