Life Inversion Field (UA)

An aura radiates from you in a 30-foot Emanation for the duration. When you create the aura, you regain 4d8 Hit Points. Whenever you regain Hit Points, you can choose a creature you can see in the aura and force it to make a Constitution saving throw. On a failed save, the creature takes Necrotic damage equal to half the amount of Hit Points you regained (round up). A creature makes this save only once per turn.

Using a Higher-Level Spell Slot: The healing increase by 1d8 for each spell slot level above 4.