Delayed Blast Fireball

A beam of yellow light flashes from your finger, then condenses to linger at a chosen point within range as a glowing bead. When the spell ends, the bead blossoms into a 20-foot-radius Sphere of fire. Each creature must make a Dexterity save, taking 12d6 Fire damage on failure, half on success. Damage increases by 1d6 for each round you delay.

Base damage increases by 1d6 per slot level above 7.