Culling Presence

For the duration, you are surrounded by a 30-foot Emanation of soul-siphoning energy. The Emanation is always one light level lower than the area around it: Bright Light to Dim Light, Dim Light to Darkness. At the start of each of your turns for the duration and when you cast the spell, each creature of your choice in the Emanation must make a Constitution saving throw. On a failed save, a creature takes 2d12 plus your spellcasting ability modifier Necrotic damage and gains one level of Exhaustion. If a creature is reduced to 0 hit points by this spell, it dies. Keep track of how much damage is dealt as well as how many creatures die. At the end of the spell, you regain a number of hit points equal to half the amount of damage dealt by this spell plus the number of creatures killed by the spell.