Unarmored Damage Reduction (5e Class Feature)
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Unarmored Damage Reduction
While you are not wearing armor, your Armor Class equals 10 + your Dexterity modifier. While you are using this AC, you have a damage reduction value equal to your Constitution modifier. You can use a shield and still gain this benefit.
This class feature replaces the Unarmored Defense feature of the base barbarian class.