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Taur-nu-Fuin (Dorthonion)

"To North there lay the Land of Dread/whence only evil pathways led/o’er hills of shadow bleak and cold/or Taur-na-Fuin’s haunted hold/where Deadly Nightshade lurked and lay/and never came or moon or day."
Canto I, Lay of Leithian

After the Dagor Bragollach, the darkness of Morgoth began to corrupt the northern forests of Dorthonion, and they came to be called Taur-nu-Fuin, the Forest under Nightshade. This name is sometimes also used for the land of Dorthonion itself, after its capture by Morgoth.

In early texts it was spelled Taur-na-Fuin, as seen in the excerpt from the Lay above.