Syphon of the Damned

You channel dark energy to drain the life force from your enemies, transferring their vitality to yourself or your allies. You take 5d10 necrotic damage upon casting the spell. This damage cannot be mitigated or reduced by any means, including resistance or immunity to necrotic damage.

When you cast the spell, choose up to three creatures within range. Each target must make a Constitution saving throw. On a failed save, a creature takes 10d8 necrotic damage. You or an ally within 60 feet regains hit points equal to the necrotic damage dealt to each individual creature. On a successful save, a creature takes half as much damage, and no hit points are regained.

On each of your turns until the spell ends, you can use your action to choose up to three creatures within range to make a Constitution saving throw. The creatures suffer the same effects as when you initially cast the spell.