Brain Drain

You attempt to temporarily sap the mental energy of a creature of your choice you can see within range. The target must make a Wisdom saving throw. The target takes 4d10 psychic damage on a failed save, or half as much damage on a successful one, and, if it fails the saving throw, its brain becomes sapped until the spell ends. This spell has no effect on constructs.

While the target's brain is sapped, whenever it casts a spell of 1st level of higher, it must make an Intelligence saving throw. On a failed save, the spell fails and has no effect unless the target chooses to take a -1 penalty to all attack rolls, saving throws, and ability checks until the spell ends.