Diminish Health

You hold out a miniature ruby flask towards your enemy. Each creature in a 15 foot cube within range must succeed a Wisdom saving throw losing all it's temporary hit points and then taking 4d8 necrotic damage on a failed save, or half as much damage on a successful one. Additionally you gain temporary hit points equal to the damage dealt.

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the damage increases by 1d8 for each slot level above 4th.