The Hill of Erech was a hill in Gondor situated at the mouth of the Blackroot Vale, far to the west of Minas Tirith. It lay near to the southern entrance to the Paths of the Dead. Upon the summit stood a smooth black globe, the Stone of Erech.
The Hill of Erech was a hill lying on the southern fringes of the White Mountains, near the source of the River Morthond.
In the Second Age, Isildur placed a great Black Stone, upon the summit of the Hill of Erech.
It was there that the King of the Mountains swore allegiance to Isildur's cause at the time of the Last Alliance. However, when he failed to fulfil his oath, he and his people were cursed to wander and haunt the hills as the Dead until they made good on their oath.
Thus, the Hill of Erech gained a sinister reputation, becoming a mysterious and eerie place, shunned by the people of the Blackroot Vale, who claimed that it was haunted by the whispering Dead.
After waiting through the long years of the Third Age, at midnight on 8 March T.A. 3019, the heir of Isildur, Aragorn, came to the Hill of Erech to hold the Dead to their oath again, promising that upon its fulfillment they would have peace. The next day they left the Hill of Erech for Calembel. Indeed, on 13 March, they held true to their oath and formed the Host of the Dead, aiding Aragorn in the defeat of the Corsairs of Umbar at Pelargir. After the battle at Pelargir, Aragorn released them from their oath and they were allowed to rest. The fate of the Hill of Erech during the Fourth Age is not known.