You have developed a keen sense of training with a shield in a cooperative combat environment, allowing you to gain additional bonuses from using a shield alongside another shield user in combat. 

Prerequisites: Shield Master

This feat:

• Grants you +2 bonus to AC while adjacent to an ally or creature friendly to you also wearing a shield
• As a reaction, you can use your shield to grant you 1/2 cover from a ranged attack if there are no allies or friendly creatures adjacent to you
• When you take an attack of opportunity, you can declare to do so with your shield. Roll a strength attack adding your proficiency bonus. If you hit, instead of dealing damage to the target, you stop its movement if it is a creature smaller or one size larger than you. Additionally, you can choose to shove the creature 5ft. in any direction.