Withering Heat

You cause a creature to be gripped by blistering heat. Choose one creature you can see within range. At the end of each of your turns until the spell ends, if the target is still within the spell's range, it must make a Constitution saving throw.

On a failure, the target takes 7d10 Fire damage, and gains one level of Exhaustion. While it has levels of Exhaustion from this spell, a creature also subtracts it's Exhaustion level from any Spell Save DC it has. On a success, a creature takes half as much damage only. A creature that has Immunity to Fire damage can't gain Exhaustion from this spell. Any levels of Exhaustion caused by this spell are removed when the spell ends.

Using a Higher-Level Spell Slot. The damage increases by 2d10 per level of spell slot above 7.