The Paths of the Dead
The Paths of the Dead are a legendary and dread passage through the White Mountains of Gondor, a road that no living man had dared to tread for centuries. It lies behind the Dark Door beneath the Dwimorberg, the Haunted Mountain, near Dunharrow in Rohan. The path is the only route that can bring Aragorn and his companions to the southern coastlands in time to intercept the fleet of the Corsairs of Umbar and save Minas Tirith from being overwhelmed. Aragorn, driven by the need for haste and the counsel of Elrond delivered through his sons, resolves to take this road, declaring, "I will take the Paths of the Dead." His companions, Legolas and Gimli, and the Grey Company of Rangers from the North, follow him of their own free will, though all but Legolas are filled with dread.
The Oathbreakers and the Curse
The Paths of the Dead are haunted by the spirits of the Men of the Mountains, who swore an oath to fight against Sauron in the service of Isildur, the heir of Elendil, in the early days of Gondor. When Sauron returned and grew in might, Isildur summoned them to fulfil their oath, but they refused, for they had worshipped Sauron in the Dark Years. Isildur then laid a curse upon them: "Thou shalt be the last king. And if the West prove mightier than thy Black Master, this curse I lay upon thee and thy folk: to rest never until your oath is fulfilled." They fled before Isildur's wrath and hid in the mountains, where they slowly dwindled, becoming the Sleepless Dead, a terror to all living things. The Hill of Erech, where the black stone brought from Númenor was set, became their trysting-place.
The Summoning at Erech
Aragorn, as Isildur's heir, is the one who can call the Oathbreakers to fulfil their oath. He leads the Grey Company through the dark caverns and the narrow ravine, pursued by the unseen host of the Dead. At midnight, they come to the Hill of Erech, where a black stone, round as a great globe, stands. Aragorn blows a silver horn and cries out, "Oathbreakers, why have ye come?" A voice answers from the night, "To fulfil our oath and have peace." Aragorn declares himself Elessar, Isildur's heir of Gondor, and commands them to follow him to Pelargir upon Anduin, promising that when all the land is clean of the servants of Sauron, the oath will be fulfilled and they shall have peace and depart for ever.
The Ride of the Grey Company
From that moment, the Shadow Host follows Aragorn, a great host of invisible shapes of Men and horses, with pale banners and spears like winter-thickets. The fear of them goes before the Grey Company, causing all folk to flee in terror, crying, "The King of the Dead is come upon us!" They pass through Lamedon and Calembel, and then into the darkness of the Storm of Mordor, lost to mortal sight. They come at last to Pelargir, where the main fleet of Umbar lies. Aragorn calls upon the Dead, and they sweep like a grey tide over the ships, filling the mariners with a madness of terror, so that they leap overboard. The Dead are the weapon of fear that breaks the enemy without a blow.
The Fulfilment of the Oath
After the victory at Pelargir, Aragorn speaks to the Dead Men, saying, "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 stands out before the host, breaks his spear, and casts it down. He bows low and turns away, and the whole grey host draws off and vanishes like a mist driven back by a sudden wind. The Oathbreakers are released from their long curse, and Aragorn, with the freed captives and the gathered men of Lebennin, takes the black fleet and sails up the Anduin to the Harlond, arriving in time to turn the tide of the Battle of the Pelennor Fields.