Armor of Kanchelsis

Blood pours from your wounds and gathers at your target forming a set of crystalline armor around them. Take 1d8 of necrotic damage then the target gains a bonus to AC equal to half the casters proficiency bonus.

If the target is hit while the spell is active they can use a reaction to end the spell early and shatter the armor. Each creature within 10ft of the target must make a dexterity saving throw against the casters spell DC. On a failed save they take 1d8 of piercing damage or half as much on a successful save.

At Higher Levels: At every level past level 1 add 1d8 of piercing damage to the damage done when the spell ends early.