Devastator

By expending all a number of spell slots and paying half your current hit points, you can choose a number of creatures that you can see up to the number of spell slots used that will ignite in black flames.

Every creature affected must make a Constitution. On a failed save, each creature takes magical fire damage equal to half their maximum hit points. On a successful save, the damage is halved.

At Higher Levels: If cast using higher spell slots, the number of creatures increase depending on the level of spell slots used. Using a level 2 spell slot can add up to two creatures that can be targeted.