Realm of Ossiriand
Forest of Brethil
Brethil (elvish for ‘beech’) was a cluster of woodlands and the realm of the Haladin during the First Age of Middle-earth. The forest bordered by Dorthonion and was the northwest border of the Kingdom of Doriath, and lay between the rivers Teiglin (west) and Sirion (east). It was a dense, sparsely populated Beech forest.
Brethil was probably originally part of Doriath during most of the Years of the Stars. When the Girdle of Melian was set after the First Battle, the Forest of Brethil was not included in it and was for the most part unsettled.
When Men came into the Beleriand, King Thingol gave his permission for some of their peoples to settle there so long as they defended it. It was to Brethil that the House of Haleth removed after dwelling east of the river Gelion, settling mainly on the Hill of Amon Obel where upon stood Ephel Brandir, the main feature of the forest. They defended it from the orcs until the late fifth century of the First Age of the Sun, when much of their number was lost including their Lord Handir in a raid by the enemy. Some Drúedain also dwelt there.
The Haladin came to Brethil from the lands of Caranthir by way of Estolad. They had endured much hardship upon their long journey, but began to recover and multiply in the isolated forest. There they formed an alliance with Elu Thingol, King of Doriath.