Verdal's Delayed Blast Fireball

At the point of a finger, a deep amber orb around 5 inches in diameter appears at the location, radiating an intense heat. These orbs can be detonated at the will of the caster, and can be maintained indefinitely. Each creature in a 20-foot-radius sphere centered on the orb 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 12d6. If at the end of your turn the bead has not yet detonated, the damage increases by 1d6.

If the glowing bead is touched before the interval has expired, the creature touching it must make a Dexterity saving throw. On a failed save, the spell ends immediately, causing the bead to erupt in flame. On a successful save, the creature can throw the bead 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.

Verdal's Chronomania: This unique version of Delayed Blast Fireball is held under a unique style of concentration, where these beads will be dispelled if the caster takes enough damage to fail their concentration check, but they do not actually require the casters "concentration",  meaning the caster can create as many of these fireballs as needed so long as they have the spell slots for it. The stacking damage multiplier has no theoretical limit.

At Higher Levels. When you cast this spell using a spell slot of 8th level or higher, the base damage increases by 1d6 for each slot level above 7th.