Blazing Heat in the Sky

Reaching out to the sky, the caster charges vast amounts of magic, focussing them into a 100 ft diameter circle up to 300 ft above a point of your choosing. Upon completing the incantation, it discharges in a rain/hail of white fire and burning brimstone. Anything within the area of effect does not benefit from cover other than total cover. Fire resistance is ignored.

Each creature within the target area must make a Dexterity saving throw. A creature takes 10d10 fire damage and 10d8 acid damage as well as being ignited on a failed saving throw, and half as much damage on a successful one. On a successful saving throw, all targets roll a d4; unless a 1, all are set ablaze regardless.

The fire and brimstone damage the surroundings.

If a cleric or a paladin casts this spell, it automatically deals additional 10d4 Radiant Damage. A wizard gains this effect only if rolling 3d6 to a 3, 4, 7, 12 or 18. Creatures made of Fire only receive Acid (and Radiant) damage, which is halved, and cannot receive Condition Burning.