Deny the Witch

Calling upon the divine authority of the God-Emperor, you deny the unnatural power of witches, sorcerers, and other foul magic users. When a creature within range attempts to cast a spell, you can use your reaction to attempt to interrupt the casting. The target must make a Charisma saving throw.

• On a failed save, the creature's spell fails, and they are struck by divine retribution, taking 2d6 radiant damage as the spell fizzles and burns away in the holy light of the God-Emperor. Additionally, the creature has disadvantage on saving throws against your spells until the end of its next turn.
• On a successful save, the creature completes its spell, but its next attack or saving throw related to the spell is made with disadvantage.