As you stretch out your arm, you siphon both natural and magical flames. As a reaction you absorb 4d8 fire damage for each creature in a 10-feet-radius sphere.  All fire in this area is distinguished. Also, for the next spell you cast that deals fire damage, you add an additional 2d8 fire damage. 

At higher levels. When you cast this spell using a spell slot of 4th level or higher, the damage negation increases by 2d8, the radius increases by 10 feet and the extra damage increases by 1d8 for each slot level above 3rd.