The Ered Mithrin Bastion can be constructed on outposts when playing as the Iron Hills.You can recruit 's here. The Ered Mithrin, also called the Grey Mountains, are a mountain range north of the Lonely Mountain encompassing the area of Withered Heath, infamous for its dragons. The Iron Hills were once a part of the Grey Mountains, but this mountain range was broken in the First Age in the War of Wrath.