[Graeme Dice]

Apostacy is quite nice as it is essentially a low level, low fatigue charm spell, which specifically targets the most dangerous units to your undead troops. It goes after priests which have a tendency to banish your troops.

The only real problems with BE Ermor's mages, is that they don't have a good communion slave, that they like to cast the single undead boosting spells an awful lot instead of things like nether dart, and that they are quite expensive for their low level magic skills.