What to do about Ermor ....

[Taqwus]

Regarding money, you could research Construction 8 and then forge the Alchemist's Stone, which is a bargain if you were already planning to research that high in that path. You could also be sure to methodically cast Gnome Lore and Auspex to get every Last earth and fire gem site.

Dominion is important to Ermorian troops; he won't get any autogenerated troops in hostile dominion, if memory serves. OTOH, a sane Ermorian player (not necessarily including the AI) will normally take a high dominion, and will attempt to protect his temples with fortresses and significant garrisons or at least reaction forces. On the other hand, Ermor normally has trouble preaching.

You could attempt to siege/preach him out in conjunction with raids to destroy unprotected temples. It may take a shorter time than you think if you can build Gate Cleavers or Wall Shakers, as Jotuns are strong and mindless undead are heavily penalized at castle maintenance.