Weavejinx

You reach into the magic of another creature, and attempt to curse their connection to spells. You and the creature both make contested ability checks using your spellcasting ability modifiers. The creature's saving throw becomes cursed for 1 minute. Whenever the cursed target casts a spell of 1st level or higher they take damage equal to the spell's level + their spellcasting ability modifier. If this damage causes them to fail a Concentration saving throw to maintain concentration on a spell, they have disadvantage on the save.