Eldritch Erosion

Sneak Attack +4d6, Knowledge (arcana) 1 rank,

Your successful sneak attack reduces your target's spell resistance and power resistance by 5 (minimum 0) for 10 rounds. If you use this feat a second time on a target before the ten rounds have elapsed, the effect of the first expires. using this reduces your sneak attack damage by 4d6

Your successful sneak attack reduces your target’s spell resistance and power resistance by 5 (minimum 0) for 10 rounds. If you use this feat a second time on a target before the ten rounds have elapsed, the effect of the first expires. using this reduces your sneak attack damage by 4d6

Your attack can weaken a foe’s resistance to magic.