How do I fight ermor?

[Taqwus]

Growth is, what, 0.3% per turn per point of Growth? Even if there's a 1000 people left rather than 0, well, that's not much compared to an Ashen Empire dominion that kills up to 50% population per turn depending on strength. It's wrecked.

You'd be better off with Luck +3 and praying that the random number generator blesses you with an immigration event, then waiting the eternity it'd take to get something back up. Basically the pop drop is a one-way trip unless that happens, or you're using a mod to dramatically boost Growth scale power.

Ravens might have helped; they eat corpses, which might be helpful if he used Carrion Reanimation (reanimates up to 100 corpses per cast) or stops to reanimate, or used his own Raven Feast to eke out a few more death gems (not that this normally yields much IIRC).