Magic Slayer

Whenever you are in close range (5ft) from someone who uses spells, you get a few perks. If they cast any spell, you can attack them with your reaction, and if they cast it against you, your saving throw will be at advantage. Not to mention that, if they have any spell on concentration, your attacks will force their concentration saving throws to be at disadvantage. You can become the ultimate menace against a spellcaster with this (and if you combo it with Sentinel too).