Once per turn, creatures provoke an opportunity attack from you when they enter your weapon’s reach.
If you are 6th level or higher, when you hit a creature with an opportunity attack, it loses its remaining movement, though it can dash to move further. Additionally, once on your turn when you use an action to make a weapon attack with a weapon from the spear group, a glaive, a halberd, a quarterstaff, or a similar weapon based on GM discretion, you can make an additional melee attack with the opposite end of the weapon. This attack has no reach and uses the same ability modifier as the primary attack. The weapon’s damage die for this attack is a d4, and it deals bludgeoning damage.