Shielding Strike

When wielding a melee weapon in one hand and no other weapons, you master the art of using your strikes to defend yourself. If a creature hits you with a melee attack, you can use your reaction to add your proficiency bonus to your AC for that attack, potentially causing it to miss you. If the attack misses due to this increase, you can make an opportunity attack against the attacker using the same weapon. This opportunity attack does not consume your reaction for the next turn.

You can use this feature a number of times equal to your Dexterity modifier (a minimum of once). You regain all expended uses when you finish a long rest.