[Edi]

Impossible to do it that way currently via a mod, because the mechanic is not unlocked (if it exists in the first place). However, the secondary effect of Ulm's black halberds (Guardians and Ghoul Guardians in MA & LA respectively) does sacred only damage, though fatigue only. Aoe 1 AN fatigue hit, so in large numbers it becomes brutal quickly.

That effect can be modded into other weapons.