Mage Slayer (Variant)

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

• When a creature within 30 feet of you casts a spell, you can use your reaction to make a one attack against that creature.
  
  
• Creatures you attack have disadvantage on the saving throw they make to maintain their concentration.
  
  
• You have advantage on saving throws against spells.