The Ancient Alliance
Originally The Alliance comprised of the Crag Mountain Dwarves (of course) & the Duergar. This unlikely pairing of races was the driving force behind the resistance to the Hoodwraith plans for domination of the ancient world.
The first war came to an end when the Hoodwraith were imprisoned in their crystal globes. Legend does not say how this was achieved; it may be that each race in the Alliance closely guarded their technologies & stratagies in an attempt to prevent ‘the other side’ from becoming stronger. The old secrets were buried deep & were ultimately forgotton by the majority of the sentient races.
Duergar, who show disdain for almost everybody (including other Duergar) kept the first Alliance due to their absolute terror of the wraith. The New Alliance originally included The Duergar but due to their extreme views & unpredictability they were thrown off at an early stage (or perhaps abandoned it, seeing other races getting involved as weakening the resistance?).