Mage Slayer

You have practiced techniques useful in melee combat against spellcasters, gaining the following benefits:

• When a creature within 5 feet of you attempts to casts a spell, you can use your reaction to make a melee weapon attack against that creature. This attack happens before the spell resolves. If the spell has a Concentration requirement, the caster must make a Concentration check in order to cast the spell. If they fail the Concentration check, the spell is not cast, and the spell slot is wasted.
• When you damage a creature that is concentrating on a spell, or attempting to cast a spell that requires concentration, that creature has disadvantage on the saving throw it makes to maintain its concentration.
• You have advantage on saving throws against spells cast by creatures within 5 feet of you.