Laeral's Crowning Touch

You place a curse on the subject. A creature that can cast arcane spells takes a -4 penalty on its saving throw. Any time the target casts a spell, he gains a number of negative levels equal to the level of the spell being cast. (The spell he just cast functions normally at the caster level he possessed before he received the negative levels for casting that spell.) This effect is cumulative and lasts as long as the crowning touch lasts.
Range: Touch
Sor 9, Wiz 9

From: City of Splendors: Waterdeep