Chain Fireball

A bright streak flashes from you to a point you choose within range and then explodes with a low roar into a fiery explosion. Each creature in a 10-foot-radius Sphere centered on that point makes a Dexterity saving throw, taking 10d6 Fire damage on a failed save or half as much damage on a successful one. Four more bright streaks fly from the center of the explosion to a point 20 feet in a cardinal direction, exploding at that point. each creature in a 5 foot radius sphere centered at each of the points makes a dexterity saving throw, taking 2d10 fire damage of a failed save or 

Flammable objects in the area that aren’t being worn or carried start burning.

Using a Higher-Level Spell Slot. The damage increases by 1d6 for each spell slot level above 3.