Defile Healing

You attempt to reverse the energy of a healing spell so that it deals damage instead of healing. If the healing spell is being cast with a spell slot of 5th level or lower, the slot is expended but the spell restores no hit points. In addition, each creature that was targeted by the healing spell takes necrotic damage equal to the healing it would have received, or half as much damage with a successful Constitution saving throw. 

At Higher Levels. When you cast this spell using a spell slot of 8th level, it can reverse a healing spell being cast using a spell slot of 6th level or lower. If you use a 9th-level spell slot, it can reverse a healing spell being cast using a spell slot of 7th level or lower.