Essence Transference

You use some of your vitality to heal another target’s wounds, taking 4d8 necrotic damage. This can’t be prevented or reduced. One target of choice that can be seen within range heals a number of hit points equal to 2 x the damage you take.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d8 for each slot level above 3rd.