Chaos Fireball

Art of the Flame of Chaos, from Ancient Aureate. Hurls a great fireball.

Chaotic flame melts even great boulders, and creates a brief surge of molten lava on impact.

The Witch of Aureate and her sisters birthed the Flame of Chaos, but it devoured them along with their home, leaving just her warrior sons. 

A bright streak flashes from your pointing finger to a point you choose within range and then blossoms with a low roar into a massive explosion of flame. Each creature in a 30-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 10d10 fire damage on a failed save, or half as much damage on a successful one. The explosion generates so much heat that the ground instantly liquefies and leaves the affected area as extreme terrain. Every creature that starts its turn inside the pool of lava takes 8d6 fire damage at the end of their turn. The lava pool remains until cooled down by a spell of one lever higher. Normal water will not cool the lava. If a 9th level Chaos Fireball is cast, the only way to remove the lava pool would be a Wish spell. 

The fire and lava spreads around corners. It ignites flammable objects in the area that aren't being worn or carried.

At Higher Levels. When you cast this spell using a spell slot of 7th level or higher, the damage increases by 1d10 (and 1d6 for the lava pool) for each slot level above 6td.