Ball-O-Fire less broken

Choose a point within range imagine a fire in you hand then throw the imaginary flame and then with a roar the area blossoms into an explosion of flame. Each creature in a 50-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 4d6 fire damage on a failed save, or half as much damage on a successful one.

This is exceedingly rare magic (end game) and the user must have great imagination mind napalm requires understanding how to make physical napalm and most find a way to convert the physical stuff into their mind dm can figure it out 

failure of the user can burn their hand or place the ball-o-fire any where in the known universe.

It ignites flammable objects in the area that aren't being worn or carried.

is less broken and can be used in normal-ish games