Masterful Defence

Your years of practice as a sentinel have granted you new ways to defend your allies in combat through your refined defensive style. You gain the following benefits:

• Creatures of your choice within 5 ft to either side or behind you gain a +1 bonus to AC.
  
  
• When you hit a creature with an opportunity attack, the creature's speed becomes 0 ft for the rest of the turn.
  
  
• When a creature within 5 feet of you makes an attack against a target other than you (and that target doesn't have this feat), you can use your reaction to make a melee weapon attack against the attacking creature.