Armor of Frost

Bewitching the air around a creature in range, you envelop them in a shimmering set of frosty armor. The creature gains a unique pool of 30 temporary hit points that are separate from temporary hit points of any other source; these hit points may only absorb damage from spells or magical effects. While the armor persists, the creature has resistance to fire and cold damage, and has advantage on Constitution saving throws to resist cold effects.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the temporary hit points increase by 10 for each slot.