Staff Master

While you are wielding a bo staff, club, greatclub, or quarterstaff and no other weapons, you gain the following benefits:

• +1 Strength or Constitution to a max of 20.
• As a bonus action on your turn, you can take a defensive stance, gaining a +2 bonus to AC until the start of your next turn.
• As a bonus action on your turn, you can make a melee weapon attack against a creature no more than one size larger than you. On a hit, you deal half damage but instead push the creature 5 feet or knock it prone.
• The first time each turn you score a critical hit on a creature, it is incapacitated until the end of its next turn.