Beshaba's Bane

Up to three creatures of your choice that you can see within range must make Charisma saving throws. Whenever a target that fails this saving throw makes an attack roll, skill check, or a saving throw before the spell ends, the target must roll a d4 and subtract the number rolled from the attack roll or saving throw. If this brings the total down to one or less, then they will critically fumble the roll. 

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, you can either target one additional creature for each slot level above 1st. Alternatively, you can increase the type of die subtracted from the enemy's roll for each 2 slot levels above 1st