Mage Scourger

You have improved in your studies and practice in the art of warfare against spellcasters, resulting in the following benefits:

• You have advantage on saving throws against spells cast by creatures.
• When you see or hear a creature within 30 feet of you begin to cast a spell, you can use your reaction to make a special weapon attack against the creature. On a hit, the target must make a concentration check as if they were concentrating on a spell. On a failure, the spell fails, and any spell slot that would be expended in the casting is wasted. You can use this reaction a number of times equal to half your proficiency bonus (rounded down) and regain all uses when you complete a long rest.