Or you can just cast earth power (as mentioned) bringing them up to e3 without wasting gems.
If i was you i would (yes i do suggest this to everyone
) i would use my pretender to summon a death mage and then use him to crank out black servants (cheap, stealthy, ethereal, lifedrain) for raiding and spectres (basically the same but more expensive and with magic for buffs) to hunt small armies (or if you send groups they could possibly do better) and equip them with cheap items (protection, strength boosters and vrs most troops fear are all top priorities) from smiths and some different items (special shields, horror helms, luck pendants ect) from summoned mages or your pretender.