Bad homebrew, please ignore

You launch a streak of light from your pointing finger that combusts into a giant burst of flame. However, an illusion of the flame precedes the real flames, throwing off anyone's attempt to avoid the fire. Each creature in a 20-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 8d6 fire damage on a successful save, or half as much damage on a failed one.

The fire spreads around corners. It ignites flammable objects in the area that aren't being worn or carried.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd.