Annihilation

You make a butterfly-shaped drawing in the air. Black flames sprout from the drawing, giving life to it. The butterfly grows to the size of a huge creature and flies in a 1,000 feet long and 120 feet wide line. Each creature in the line must make a Constitution saving throw (DC 20 + spellcasting ability modifier). A creature takes 50d6 necrotic damage on a failed save, or half as much damage on a successful one. If a target is reduced to -10 hit points or less (or a construct, object, or undead is reduced to 0 hit points), it is utterly destroyed as if disintegrated. Not even a trace remains.