Eldritch fire

A bright streak flash from your pointed finger and a green crackling fire around. Each creature in a 10-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 5d6 fire damage on a failed save, or half as much damage on a successful one. Only hostile creatures take damage.

it spreads to every flammable object 

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.