Eryn-in-Úanhoth

Our esteemed colleagues in the Guild of Cartographers seem to have plucked the Quenya name "Aron ''Úvanimin" from thin air, as a child would a butterfly. None of '' the local countrymen with whom we spoke had ever heard it  ''applied lo their fabled wood. Indeed, they were loath to mention '' the wood by name at all, but when pressed on this point the name  they preferred was Sindarin, Eryn-in-Úanhoth, also meaning ''"the Wood of Monsters".' -Findegil of Gondor

Eryn-in-Úanhoth' was a remnant of the primeval forest that once covered the Nan Lefnui, before the tree-felling Númenóreans set foot on the shores of Middle-earth, greedy for timber. This ancient stand of beeches, scarcely ten miles from end to end, touched the eastern bank of the upper Lefnui near to its confluence with the Nimthond, where it bent southward towards the sea. The wood had been left undisturbed by Daen and Dúnadan alike, and few would pass willingly beneath its eaves, fearing the malice that lay within. What power actually lurked within the shadow of Eryn- in-Úanhoth was the stuff of endless local tales and legends (some more credible than others), but those who had ventured into the wood and came out again to tell of it intimated that the trees appeared to be sentient and indiscriminately hateful of all speaking peoples. An arm of the Len Lefnui passed through the edge of the wood as it followed the course of the river, but few travelers took this path, unless they were bound for the Cirith Nimrais to the north.