Bluestone's Thunderous Blast

You extend your hand and the twigs burst into flame and fly towards a point of your choosing within range, detonating with a fiery blast of thunder that can be heard up to 100 feet away. Each creature in a 20-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 6d8 fire damage on a failed save and is knocked prone, or half as much damage on a successful one and is not knocked prone.

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 5th level or higher, the damage increases by 1d8 for each slot level above 4th.