Driddle's Regenerating Mage 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.

For the spell's duration, the target regains hit points equal to your spellcasting ability modifier at the start of each of its turns.