The Balrogs were in origin Maiar, of the same order as Sauron or Gandalf. They were primordial spirits of fire that had allied themselves with Melkor in ancient times, and became the most feared of his servants, especially during the Wars of Beleriand in the First Age. In The Fellowship of the Ring, the Fellowship ventured through Moria and were attacked in the Chamber of Mazarbul by Orcs and the Balrog. Gandalf faced the Balrog at the Bridge of Khazad-dûm. He slew the Balrog but perished himself at the same time — to be sent back as the more powerful Gandalf the White.
