Morthond
From Tolkien Gateway
The Morthond, also called Blackroot, was counted as second of the Seven Rivers of Gondor, named so because its source was in the dark caverns of the Dead Men.
It began on the southern edges of the Dwimorberg at the end of the Paths of the Dead in the White Mountains, then flowing past the ancient fortress of Erech, it went on its long journey south, avoiding the Green Hills of the Pinnath Gelin while picking up its tributary Calenhir, and entering the sea at Edhellond.
Aragorn and the Grey Company emerged from the Paths of the Dead in Morthond's vale and followed the river briefly to Erech on their way to southern Gondor.
