You assault the mind of a creature you can see within range.  The target must make an Intelligence saving throw.  A creature with an Intelligence score of 2 or lower can’t be affected by this spell.  The target takes 8d6 psychic damage on a failed save, or half as much damage on a successful one. 

After a failed save, a target has muddled thoughts for 1 minute.  During that time, it rolls a d4 and subtracts the number rolled from all its attack rolls and ability checks, as well as its Constitution saving throws to maintain concentration.  The target can make an Intelligence saving throw at the end of each of its turns, ending the effect on itself on a success. 

At Higher Levels.  When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above third.