Taur-nu-Fuin was a name for the northern parts of Dorthonion, and sometimes for the forest as a whole after it was corrupted by Morgoth after the Dagor Bragollach. The kingdoms of Dorthonion were destroyed at that point, including Ladros and the realm of Angrod and Aegnor. Barahir remained as an outlaw in Taur-nu-Fuin, and after his death Beren his son dwelt in this forest for several years, before crossing the Ered Gorgoroth and forsaking Dorthonion to its captors. Then it was truly wholly "under nightshade".
After Sauron was defeated by Huan in their battle upon Tol-in-Gaurhoth he took the form of a vampire and fled to Taur-nu-Fuin, filling the forest with horror.
After the formation of the Union of Maedhros, in 468, Dorthonion was briefly cleared of evil when the Orcs were driven out of all the northward regions of Beleriand. At some point before 489, though, it had returned to a place so full of dread and evil that not even the Orcs would go through it save by a single Orc-road, and even then only when in great need and haste.
After Túrin was captured upon Amon Rûdh, he was taken by the Orcs through Taur-nu-Fuin northwards on the Orc-road. In those woods the pursuing Beleg came upon Gwindor, who told him of seeing Túrin being whipped and driven towards Angband. Together the two Elves followed the orcs out onto the barren dunes of Anfauglith.
