Unending Curse

You invoke the darkest of curses against a group of enemies, weakening them forever. Choose a spot you can see. Any creature within 30 ft. of that point must make a DC 20  Intelligence saving throw (add 1 for each person above 5 helping cast the spell). On a failed save, these creatures lose all class levels (if any), and can never take levels in that class again. If the creature is multiclassed, than you can choose if you want to remove all levels from one class or half of all total class levels (rounded up). This spell cannot be broken by anything short of a wish spell.