Improved Duelist

When you are wielding a finesse weapon with which you are proficient and another creature hits you with a melee attack, you can use your reaction to focus your defenses against that creature's attacks. You gain an AC bonus until the start of your next turn or until one of the creature's attacks damage you. Your AC increases by your proficiency bonus for the first attack and drops by 2 for every subsequent attack the creature takes against you on its turn, to a minimum of your original AC.
If your strength score is at least 13, you can use this feature with any melee weapon which has the versatile property.