Dorthonion encompassed the pine-clad uplands of northern Beleriand. The highland measured 70 leagues by 20 leagues, and was thickly wooded and extremely mountainous.

The land was occupied by the First House of the Edain until after the Dagor Bragollach - when Dorthonion was abandoned by all but Barahir and his men. The land itself became corrupted, and became known as Taur-nu-Fuin - "Forest under Nightshade", and Deldúwath - "Deadly Nightshade".
Encyclopedia entry originally written by atalante_star