Ticking Bomb

You mold and infuse the gunpowder and sulfur with latent power into a small glowing bead for the duration. When the spell ends, either because your concentration is broken, the bead has impacted a surface or creature, or because you decide to end it, the bead blossoms with a low roar into an explosion of flame that spreads around corners. Each creature in a 15-foot-radius sphere centered on that point must make a Dexterity saving throw. A creature takes fire damage equal to the total accumulated damage on a failed save, or half as much damage on a successful one.

The spell's base damage is 4d6. If at the end of your turn the bead has not yet detonated, the damage increases by 1d6.

The bead can be thrown up to 40 feet. When it strikes a creature or a solid object, the spell ends, and the bead explodes.

The fire damages objects in the area and ignites flammable objects that aren't being worn or carried.

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the base damage increases by 1d6 for each slot level above 2nd.