Akron's Infernal Rebuff

You Speak with a commanding voice, and pull upon the flames of Hel to grant an exchange. Within a cone, 20 ft long and 10 ft wide, the first 3 creatures hit by the pulse will receive 3d10+[spell modifier] in health returned to them. The same amount is dealt in fire damage to the next 3 creatures.  

If there aren't enough creatures make this an even exchange, the excess damage is dealt back to the caster in [necrotic] damage.

[A deal is struck and an exchange must occur.]

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the health/damage increases by 2d10 for each slot level above 1st.