Magic resistance (or MR) is a stat that all units have, including minions, monsters, and buildings. Increasing magic resistance reduces the magic damage the unit takes. Each hero begins with some magic resistance which may increase with level. You can gain additional magic resistance from abilities, items and talents. Magic resistance stacks additively.
Incoming magic damage is multiplied by a factor based on the unit's magic resist:
Magic Resistance > 0 : Damage multiplier = (100 / [100 + Magic Resistance])
Magic Resistance ≤ 0 : Damage multiplier = 1.0
- 25 MR -> 0.8 incoming magic damage (20% reduction, +25% effective health).
- 100 MR -> 0.5 incoming magic damage (50% reduction, +100% effective health).
- -25 MR -> 1.0 incoming magic damage (0% reduction, +0% effective health).