About the Balrog, wasn't he "awakened" or "roused" when the Dwarves kept mining deeper and deeper?
I kind of wondered if it didn't represent the monster "Greed"?
Sure love to hear comments - or corrections.
Balrogs were originally Maiar (same as Sauron or Gandalf). See Encyclopedia of Arda for more details. If memory serves, Durin's Bane was imprisoned in Moria and the Dwarves accidently released it by mining too deeply.