I've tried #73 and #285 effects (separatly and at the same time): using a flat value of 0. But in-game, my warrior always inflicts damages.
Effect 250is a little odd for me: I made searches, and the damage modifier is always set to 20 (to inflict maximum amount of damages according to the various spells descriptions)- I guess it's not really useful for my purpose
If you have a tip to make my character inflict 0 damage at each strike, juste tell me!