You flourish a weapon you are proficient with used in the casting of this spell, then whirl around igniting it in the whirling conflagration. Make a melee weapon attack against each target within 15 feet. Each target takes 6d6 fire damage on hit, or half as much on a miss.

At Higher Levels: When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each level above 3rd.

Source: Kibble's Casting Compendium