Black Blade

You create a representation of Maliketh's black blade, channeling Destined Death and swinging the blade twice. Make two melee spell attacks against one creature or two separate creatures within range. On a hit, a target takes 6d10 necrotic damage. This damage cannot be reduced in any way. When a creature takes this damage, its maximum number of hit points is reduced by the same amount until it completes along rest.
Regardless of whether it hits or misses, each attack releases an arc of light in a line 10 feet wide and 60 feet long. Each creature in the line must make a Dexterity saving throw. A target takes 6d6 radiant damage on a failed save, or half as much on a successful one.
Each creature that takes damage from this spell takes an additional 2d10 necrotic damage at the start of its next turn as Destined Death saps its life away.