Magic Resistance
You are less likely to be affected by magic. Subtract your Magic Resistance from the skill of anyone casting a spell on you, and add it to your roll to resist any spell that offers a resistance roll. For instance, if you have Magic Resistance 3, wizards have -3 to cast spells on you and you get +3 to resist. In addition, you may roll against HT + Magic Resistance to resist the effects of magical elixirs. You cannot "turn off" this advantage to let friendly wizards cast spells on you (e.g., to heal you) or to benefit from helpful elixirs!
Magic Resistance only interferes with spells cast directly on you. It provides no benefit against Missile spells (which are cast on the wizard's hand and hurled at you), attacks by magic weapons, or information-gathering spells that aren't cast directly on you. It also has no effect on supernatural powers other than magic; e.g., divine miracles, psionics, or the innate powers of spirits. Magic Resistance, and its precise level, can be recognized by any mage who looks at your aura, or by anyone who casts a spell on you.
You cannot combine Magic Resistance with Magery. If you have even one level of Magic Resistance, you can't cast spells at all (although you can still use magic weapons).
Special Enhancements
Improved: You Magic Resistance does not interfere with your own ability to cast spells. This allows you to possess both Magery and Magic Resistance. +150%.