[Cirdan]

Originally Posted by Nerwen

No– at least not if we go by the Silmarillion– Morgoth "reared the threefold peaks of Thangorodrim" above Angband only after his return to Middle-earth.

Indeed, and that would be a valid point but...I'm not convinced that "Thangorodrim" isn't just a synonym for the realm of Angband -in the Appendices, that is. It's the way it is used in the there several times that led me to some doubt, and to my question. Consider this:

"Thereafter followed the hopeless war of the Eldar and the Edain against Thangorodrim, in which they were at last utterly defeated."

"Against" his volcanic peaks? No, against his evil realm, Angband! This led me to suspect that the LOTR Appendices were written before (or after) some of the Silmarillion, and Tolkien hadn't decided yet exactly which names would be applied to what. Perhaps the Histories would clear that up.

Regardless, Durin's Bane must have been a refugee from the War of Wrath. Of that this is written in the Silmarillion:

"The Balrogs were destroyed, save some few that fled and hid themselves in caverns inaccessible at the roots of the earth"

So besides under Moria we can find a couple more elsewhere! Any guesses? Ash Mountains? How about deep into Aglarond or under Mindolluin!

This would seem to be more "proof" in Letters of J.R.R. Tolkien:

"The Balrog is a survivor from The Silmarillion and the legends of the First Age. So is Shelob. The Balrogs, of whom the whips were the chief weapons, were primeval spirits of destroying fire, chief servants of the primeval Dark Power of the First Age. They were supposed to have been all destroyed in the overthrow of Thangorodrim, his fortress in the North. But it is here found (there is usually a hang-over especially of evil from one age to another) that one had escaped and taken refuge under the mountains of Hithaeglir (the Misty Mountains)."(Letter 144)

It's likely that he is speaking of the First Age of the Sun...although the War of the Powers was in the "First Age" too -First Age of the Stars.