Impenetrable

A Strength score of 16+ and the Heavy Armor Master feat

Your ability to deflect and shield yourself from harm when wearing heavy armor has made you impenetrable. You gain the following benefits:

• Increase your Strength or Constitution score by 1, to a maximum of 20.

• You gain a +1 bonus to AC while wearing heavy armor.

• As a reaction when you suffer a critical hit from a weapon attack, you can use your reaction to turn that attack into a normal hit. Any effects triggered by a critical hit are canceled.

• A critical hit against you must still hit your AC to become a critical hit while you are wearing heavy armor.