Pit Fighter

You've become a fierce competitor in a bloody fist fighting sport. When both of your hands are empty you gain the following benefits:

• Your Unarmed damage die increases by one size. (1d4>1d6, 1d6>1d8, etc.)
• You have advantage on Strength (Athletics) and Dexterity (Acrobatics) checks when defending against grappling and shoving (but not when escaping grapple).
• When you successfully grapple a creature as part of your action, you can attempt to perform a powerful throw as a bonus action. Make another grapple check. Upon success the grappled creature takes 1d4 bludgeoning damage, falls Prone, and the grapple ends. Additionally, the creature must succeed on a DC 10 Constitution saving throw or become Stunned until the end of its next turn.
• When a creature makes a melee attack against you and misses, you can use your reaction to attempt to grapple or shove the creature.