You can sacrifice magical energy to gain a bonus to your defenses for a short period.

Prerequisite(s): Spellcraft 9 ranks, 3rd-level mystic theurge

Benefit: By sacrificing an uncast spell or unused spell per day (for spontaneous casters) you can gain a temporary insight bonus to your armor class and Combat Maneuver Defense. Activating this ability is a move action, and the bonus you gain is equal to the level of the sacrificed spell and it lasts a number of rounds equal to your mystic theurge level. You can use this ability once per day per three levels of mystic theurge you possess.