Armor of the Magi

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 14 + its Dexterity modifier. The spell ends if the target dons armor or a shield or if you dismiss the spell as an action.

At Higher Levels. When you cast this spell using a 4th- or 5th-level spell slot, the AC increases by 1. When you cast it using a 6th- or 7th-level spell slot, the AC increases by 2. When you cast it using a spell slot of 8th level or higher, the AC increases by 3. In addition at 9th level you may cast it on one additional target.