Dark Armor

You call on a necromancer technique to weave shadows around you so as to guard yourself against harm. For the duration, you gain a +3 bonus to AC, and any creature that hits you with an attack must make a CON saving throw. On a failed save, the creature takes 1d6 necrotic damage. These benefits last for 3 rounds, starting at the end of this turn.

When you cast this spell using a spell slot of 4th level or higher, the AC bonus increases by 1 for every level above 3rd. In addition, a target that fails the CON save takes an extra 1d6 necrotic damage for each level above 3rd.