The Valaraukar was an organization of Balrogs who were created and served under the allegiance of Morgoth during the First Age. Prior to the Revolt of the Ñoldor, Kosomot was the High Captain of Angband and given the title Lord of the Balrogs.
History
During the First Age, the Balrogs of the Valaraukar were among the most feared of Morgoth's forces.