control spell

As a reaction, as someone other than you within 120 feet of you is casting a spell you may attempt to wrest control from them. You enter a contest with them using your spell casting ability against theirs. If they win this spell has no effect. If you win you get to decide the target of the spell or where it is placed. You can also use this to control a spell that is already in existence, you can change the targets of the spell or change its locations.