Wave of Essence Drain

A wave of life-draining energy emits from you. Each creature in a 40-foot cube must make a Constitution Saving throw. On a failed save, all creatures within that wave take 7d6 Necrotic damage or half as much on a successful one. Whether or not a creature succeeds or not, the wave returns to you with the hitpoints acquired. On the waves' return, you can select up to three creatures, including yourself to pour those hit points into. Any hit points in excess turn into temporary hit points for yourself and the creatures you selected.