Volt Diffusion

Holding your hands skyward, a bolt of lightning strikes you and diffuses throughout your immediate vicinity. You take 4d8 Lightning damage, and all other creatures within 15 feet of you must make a Dexterity saving throw. On a failure, a creature takes lightning damage equal to twice the damage you took. On a success, they take lightning damage equal to the amount you took. 

At Higher Levels: When you cast this spell using a spell slot of 5th level or higher, the damage increases by 1d8 for each slot level above 4th.