Martyr's Counter

Your grit and determination in combat is impressive. As a bonus action, you can sacrifice a part of your body by exposing it to one enemy within melee range, allowing the enemy to attack during your turn.

You are, however, prepared and are able to catch the attack with one hand, taking normal damage, and trap your enemy's weapon. As a result, you are able to: take your attack(s) with advantage and a hit is an automatic critical. 

If your enemy critically hits you, this bonus action is cancelled. Once your round is complete, you release your enemy's weapon.