Enhanced Mage Armour

You touch a willing creature who isn't wearing armor, and a heightened, protective magical force surrounds it until the spell ends. The targets base AC becomes 16 + its Dexterity modifier. All weapon attacks are at disadvantage if the attacker is within 5 feet of you. Additionally, you take no damage from magic missile. The spell immediately ends if the target dons armor or if you dismiss this spell as a bonus action.