Several changes.

in \GameMechanics\Spell\ lie the standard files with paths to icons, descriptions, names, and visual effects; the mana and resource costs are also specified there, and sometimes the damage

\GameMechanics\RPGStats\DefaultStats.xdb  line 295 <ZombieWeakeningStrike>2</ZombieWeakeningStrike> this is where the strength is changed

To clarify: can't I replace one ability's slot with another? I.e., copy the code of one and place it in the place of another? 
Thanks, I've already found it. Aaaand damn, you can't separately configure the change to attack and defense. So I take it that to change this, you'd need to dig into the executable, wouldn't you? 
Maybe there's already a mod that has an effect of purely reducing armor per hit?