Clusterbomb

A condensed ball of fire, bubbling and squirming with energy launches from your palm, and violently explodes on contact. Its volatile form releases 4 flaming bouncy orbs in a cross, that move up to 25ft, which then explode. Each creature in a 15-foot-radius sphere centered on that point, and each creature in a 10-foot-radius sphere around each orb, must make a Dexterity saving throw. A target takes 6d6 fire damage from the central explosion, and 2d6 from each orb, on a failed save, or half as much damage on a successful one.

The fire 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 of both the explosion and the orbs increases by 1d6 for each slot level above 6th.