Description needed.
Two different Balrogs - Balrog of Moria and A Balrog.
Army Encounter
Found in the Mountains?
Free Peoples: ?
Neutral:
Dark Servants: Found in the Mountains. Comparable to a dragon (better), and reported picked up by a Dog Lord army, who just moved onto it and then it joined! But the player cautioned that you'd better fight a lot, or bad things could happen (perhaps the Balrog eats the army commander?). (Bobbins)
Balrogs can encounter armies. When Free Peoples or Neutral forces are involved, they'll attack and slay a large number of troops. It isn't known whether they'll attack Dark Servant armies. GSI has confirmed that it's possible (although extremely difficult) to actually recruit a balrog into a Dark Servant army, much like recruiting a dragon. Paul Lundstroem reported having a Balrog joining his Dog Lord army by moving onto the same hex.
Balrogs will affect pop centers like dragons, positively for Dark Servants, negatively for Free Peoples, and randomly for Neutrals, though such changes are usually minor (a few points at most).