Frost Armor

You manifest the power of ice, creating a protective cold force around yourself. During this time, you gain temporary hit points equal to twice your Spellcasting Ability modifier. While you have these temporary hit points, all your weapon attacks deal additional damage equal to your Spellcasting Ability modifier as cold damage. In addition, any creature that hits you with a melee attack while you have these temporary hit points takes twice your Spellcasting Ability modifier as cold damage.

At Higher Levels. When cast as a 5th-level spell or higher, the cold damage becomes glacial.