Stagger

You’ve trained extensively to disrupt your enemies’ focus during combat. Once per turn, when you take the Attack action, you can use your melee attack to attempt to stagger a humanoid creature within range. A successful attack does the same damage as an unarmed strike, regardless of the weapon used, breaking the creature’s concentration and forcing it to drop its battle stance. 

When staggered:

• The creature’s AC is reduced by 2 until the start of its next turn
• The creature cannot use any Reactions, except previously Readied actions, until the start of its next turn

Only humanoid creatures that are Large or smaller can be staggered.