Barbed Armor

You touch a willing creature who isn't wearing armor, and a protective magical force surrounds it until the spell ends. The target's base AC becomes 13 + its Dexterity modifier. The spell ends if the target dons armor or if you dismiss the spell as an action. Any creature within 5 ft that touches or hits the target with a melee attack, takes 1d6 piercing damage, as magical barbs lash out at the attacker.