Erui

Erui was a river in Gondor. This swift-flowing river began near Mindolluin in the White Mountains, flowing south through the province of Lossarnach, where it met the Anduin about 75 miles south of Minas Tirith. Of old, it was part of the border between Anórien and Lebennin.
The main road from Minas Tirith to Pelargir crossed the Erui at the Crossings of Erui. It was not counted amongst the Seven Rivers of Gondor.
The river began near Mount Mindolluin in the White Mountains, flowing south through the province of Lossarnach, where it met the Anduin about 100 Númenórean miles south of Minas Tirith.
The Erui was located in Eastern Gondor and was the easternmost of the Five Rivers of Lebennin. It flowed through Imloth Melui and divided Upper Lebennin and Lossarnach. The Erui was the domain of the brooding River-maid known as the Lone Lady, one of the Five Sisters, though she and her sisters were widely considered a myth by the end of the Third Age. The Lone Lady had long been detached and troubled due to the blood spilled in her waters during the Kin-strife, and the invasion by Haradrim during the War of the Ring enraged her. She commanded the waters of the Erui to animate the armour of long-dead soldiers of Gondor to drive away any who approached the Crossings. She was calmed by her sisters, but not before raising the armour of Castamir himself from the riverbed.