Magic Resistance Stacking

[Narg666]

Hi everyone...

I need a help with Magic/Spell resistance stacking...

I know that Elune's Grace and Spell Damage Reduction can stack, but my problem is, I have the following:

2 Items that gives magic resistance and must NOT stack with each other...
Heroes that have a skill of magic resistance and MUST stack with those items.
Temporarily given skills that reduces or increases more magic resistance and MUST stack with every other magic resistance item/skill.

I currently have:

1 Item A that gives 15% magic resistance based on Elune's Grace
1 Item B that gives 30% magic resistance based on Elune's Grace
1 Item C that gives 35% magic resistance based on Elune's Grace

Heroes with skills based on Spell Damage Reduction

and temporarily given skills based on Spell Damage Reduction

For example:

My heroes have no base magic resistance, so 0%

0% + an item A + a skill that gives 15% magic resistance and he is affected by another skill that gives -15% magic resistance

How can I make these skills stack? They don't need to stack additively like 15+15=30, but can they stack anyway? How?

Thanks.

 

[Vladadamm]

You should increase the level of a Spell damage reduction ability when you need to change the magic resistance.