Taur-nu-Fuin (Dorthonion)
From Tolkien Gateway
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.