Polearm Master

Source: Player's Handbook

You gain the following benefits.

Ability Score Increase.
Increase your Dexterity or Strength score by 1, to a maximum of 20.

Pole Strike.
Immediately after you take the Attack action and attack with a Quarterstaff, a Spear, or a weapon that has the Heavy and Reach properties, you can use a Bonus Action to make a melee attack with the opposite end of the weapon. The weapon deals Bludgeoning damage, and the weapon’s damage die for this attack is a d4.

Reactive Strike.
While you're holding a Quarterstaff, a Spear, or a weapon that has the Heavy and Reach properties, you can take a Reaction to make one melee attack against a creature that enters the reach you have with that weapon.