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When you choose a Fighting Style you can instead choose this feat. You can’t take a Fighting Style Feat option more than once, even if you later get to choose again.

When a creature you can see attacks a target other than you that is within 5 feet of you, you can use your reaction to attempt to mitigate incoming attacks. You must be wielding a shield. You and your ally both benefit from your shield bonus until the start of your next turn as long as you remain within 5ft.