La Marignon research strategy against Ermor

[K]

You want Construction, actually. Putting Spell Focuses and Eyes of the Void on your H3s make them very good at knocking down Ermorian undead who are buffed by Ermor's special Holy magics.

If you are lucky, get a guy who can forge Crystal Matrixes and get those H3s up to H5s or H6s via Communions. Not only will the penetration increase in the Communion, but the AoE and base damage on Banishment will increase dramatically. (Crystal Shields will also give your H3/F1s a +1 Holy, so a simple H3/F1 who is your Prophet can be handed a Crystal Shield, a Crysta Matrix and am Eye of the Void and can be placed in a simple four man Communion for a whopping H7 with a +2 penetration on top of the base path penetration.... and watch the dead boys burn.)

While you are in Construction, you can also make Flambeaus(Holy Fire) and Holy Lances, as well as the Boots of Quickness to use them.