The Killing Wind of Mystra

This is a 10th level spell granted by Mystra herself.

You create a cloud of billowing vapors that blow at high speed from you through the area you designate within range. Until the spell ends, strongly acidic vapors gust around in 100 adjacent 5-foot cubes.

When the winds appear, each creature in it must make a Constitution saving throw, taking deal 20d6 points of acid damage on a failed save, or half as much damage on a successful one. A creature must also make this saving throw whenever it ends its turn in the winds.

You can reshape the area as a bonus action each round during the spell's duration if you so desire.

As a special feature of this spell, you can increase the saving throw DC at the time of casting by sacrificing more HP. For every 10 HP, you sacrifice beyond the 30 HP required to cast the spell, the saving throw DC increases by +2.