Uskius' Brainfreeze

Ooh, that's too fast- you activate a feedback weave that damages your foe as they work magic of their own. The triggering creature must make an Intelligence save: on a fail, they take 1d6+spellcasting ability modifier cold damage, and are unable to take reactions until the start of their next turn; on a save nothing happens to them.

At 5th level and 11th level the damage increases by one die, and at 17th level the target is also unable to take the Disengage action until the end of its next turn on a failed save.