Spell Resist Debuff

Trying to make a spell that debuffs spell resistance for target enemy. Have tried using things like AntiMagic Shell and setting the Magic Damage Reduction to negative value, I _think_ this might be reducing their spell resistance but, it makes them immune to spells (I have tried removing magic immune classification through trigger to see if this would help). Wondering if anyone has an idea on how to do this .

thanks!

There are two different anti-magic-shell abilities, one makes the unit comepletely imune to spells, and the other just prevents a certain ammount of magic damage. None of them actually reduces the ammount of damage taken, except if the second one can be modified to only reduce a certain percentage of the damage dealt, rather than all o9f it as it does by default. Even so, it's uncertain if the spell can take a negative value.

An alternative would be to use triggers to add a passive spell damage reduction ability to all units that have the buff, and remove it when they loose the buff.