BaleFireball

A bright streak flashes from you to a point you choose within range and then blossoms with a low roar into a fiery explosion. Each creature in a 40-foot-radius Sphere centered on that point makes a Dexterity saving throw, taking 10d6 Fire damage on a fail, or half as much on a success. The area within this sphere then burns with Balefire for 1 minute.

A creature must make a Dexterity saving throw the first time on a turn that it enters the Balefire or when it begins it's turn within the area. A creature takes 10d6 fire damage on a failed save, or half as much damage on a successful one. Any damage dealt by this spell also reduces the affected creature's hit points by the same amount. This hit point reduction cannot be undone by any means short of a Wish spell or Divine Intervention.