Spell resistance

Spell resistance was an abjuration spell that granted resistance to incoming spells.

Effect
Once cast, the spell would grant resistance to other spells, which increased with respect to their power.

In order for the recipient of spell resistance to be hit by another spell, a caster had to somehow overcome their spell resistance. A lot of this was luck based, but more powerful casters had a higher chance of overcoming another's spell resistance. For incoming beneficial spells, the creature under the effect of spell resistance could willingly accept the spells, instead of resisting them.