The Pass of Aglon
the cold defile between Dorthonion and Himring
Names
The Pass of Aglon, also called Aglon, “the narrow pass”, is the name of the great defile of the eastern marches.
Geography
The pass lay between the plateau of Dorthonion — whose border rose in very high steep walls along its western side — and the hills before Himring, to the north-east of Beleriand. It ran for about six leagues, and a cold wind blew through it continually out of the lands to the north.
History
Celegorm and Curufin heavily fortified the pass from their realm of Himlad, and Maedhros upheld the weak point from his fortress upon Himring. In the Dagor Bragollach the Orcs broke through in the Battle of the Pass of Aglon, though Maedhros recovered it for a time; and after the Nirnaeth Arnoediad the pass fell under the domination of Melkor and was garrisoned by Orcs, never to be won again.