The return of Sauron

[Boromir88]

mormegil,

If if there were more Balrog's (which is possible) I don't see them as that great of a threat as say Sauron or Melkor were.

Durin's bane was the last balrog, and Gandalf slays it...From letter 144.

But it is here found (there is usally a hang-over especially of evil from one age to another) that one had escaped and taken refuge under the mountains of Hithaeglin (the Misty Mountains).