Brainshock

You create a continuous powerful flash of colors inside a creatures mind. Choose one creature that you can see within range to make an Intelligence saving throw. If they fail, every roll the target makes that uses their intelligence ability modifier has disadvantage and deals psychic damage to the target equal to the lowest number rolled. Additionally if the target tries to cast a spell while under the effects of brainshock they must make another Intelligence saving throw. If they fail the spell isn't cast and is wasted, if they succeeds the spell is cast and brainshock ends on the target.