Bartleby's Bowling Bomb

Bringing your arm back, then rolling the sulfur-dipped ball bearing toward your for, it will grow in size to that of a 1 foot diameter ball of flaming iron that explodes when reaching a target. The ball can be detonated with a thought from the caster. Each creature in a 20-foot-radius sphere centered on the explosion point must make a Dexterity saving throw. A target takes 8d6 fire damage on a failed save, or half as much damage on a successful one.

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