[Galin]

Pedantry alert! Even three, or at most seven ever existing, according to that Balrog note.

I wonder about a possible compromise with "many" rogs existing before Utmno was broken, and . . . maybe five (?) left at the time of Curufinwe's fall and the later fall of Gondolin -- then three for the Wrathy War -- and one left before the Company arrived in Moria.

Or something else (maybe start with 7 surviving Utumno, leaving more rogs left for the WoW).