Shield Wall (5e Feat)
From D&D Wiki
Prerequisites: Proficiency with Shields
You have learned how to use your shield more efficiently. As a bonus action, you can enter a defensive stance with your shield ready to strike at enemies heading in your direction. Until your next turn, when an enemy enters your reach, you can make an opportunity attack. If you hit with this attack, the enemy's movement is reduced to 0 for the rest of its turn.
You can use your shield to protect your allies. When an enemy makes a weapon attack, you can use your reaction to make the attack target you instead.
You can take advantage of strength in numbers. When you are within 5 ft of an ally, both you and your ally gain a +1 to AC. This effect can stack with other allies with this feat.
When an enemy makes an area attack with a physical appearance (eg fireball), you can use your reaction to add your shield bonus to the saving throw. On a failed save you take half damage, and no damage on a successful save.