This tattoo depicts protective imagery and uses ink that resembles liquid metal. While you aren’t wearing armor, the tattoo grants you an Armor Class depending on the tattoo’s rarity, as shown below. You can use a shield and still gain this benefit.

Barrier Tattoo
Rarity AC
Uncommon 12 + your Dexterity modifier
Rare 15 + your Dexterity modifier (maximum of +2)
Very Rare 18

Tattoo Attunement. To attune to this item, you hold the needle to your skin where you want the tattoo to appear, pressing the needle there throughout the attunement process. When the attunement is complete, the needle turns into the ink that becomes the tattoo, which appears on the skin. If you have multiple magic tattoos, they count as a single magic item with regard to the number of magic items you can attune to.

If your attunement to the tattoo ends, the tattoo vanishes, and the needle reappears in the closest unoccupied space to you.