[Torin]

Maybe you should not underestimate the undead.
bring several (a LOT of) priests (lvl 1 is ok)
Frontline infantry (or any tough guys like vine ogres)
Archers (they often kill more undead than the priests)

if you dont deal with ermor quick you should get an ally or you could be overwelmed.

if you are, try a mass damage spell like wrathful skyes or earthquake.
Blade wind is optimal. most of the undeads are unarmed souless reanimated by priests and not the legionaries guys.

i didnt try but maybe stuff like swarm may work.