Demons of shadow and flame. Balrogs were creatures of great power and terror. Their fundamental form appeared to be that of a man of great stature, but they were cloaked in shifting shadows and they had fiery cores. Balrogs had burning yellow eyes and streaming manes that kindled with fire. Their arms were long and powerful, and they may or may not have had wings. The Balrogs' chief weapons were whips with flaming thongs. 
Balrogs belonged to the order of the Maiar - the servants of the Valar. The Balrogs were originally spirits of fire that were corrupted by Morgoth in the beginning. They dwelled in Morgoth's strongholds of Utumno and Angband in Middle-earth. When those fortresses were destroyed by the Valar in the Battle of the Powers, some Balrogs hid in the caverns below and they awaited Morgoth's return from captivity. 

