Voidstorm

You channel the powers of the void to unlock infinite potential as you begin levitating a foot above the ground and spheres of power swirl around you like a storm. A sphere of black ash swirls around you in a sphere ranging from 100ft to 150ft and a sphere of black fire surrounds you in a sphere from 20ft to 30ft, any creature that starts its turn inside of the sphere of ash makes a constitution saving throw and takes takes 1d10 fire damage and 1d8 necrotic damage on a failed save or half as much on a successful one, any creature who starts its turn within 10ft of the flaming sphere makes a strength saving throw and gets their movement halved on a failed save and also makes a constitution saving throw (DC is the casters spell save and takes 10d20 fire damage and 10d12 necrotic damage on a failed save or half as much on a successful one. 

The spells ash creates magical darkness within both the spheres and nonmagical darkness everywhere from the caster to 30ft away from the sphere of ash

You can make a constitution check to exclude creatures from the effects of the spheres with the DC being however many creatures you want to exclude X2 (+15) 

This spell both requires concentration and you cannot take turns while casting it, instead when it is your turn you can either dispel the spheres or use the spheres to attack a creature (make a ranged spell attack) and deal 5d10 fire damage and 5d10 necrotic damage. Or pulse the storm and make all creatures within it to have to succeed a strength saving throw (DC is the casters spell save) or be pushed/pulled towards/away from the caster by 10ft

If a creature doesn't fully fit inside the spheres it only takes max damage minus however many ft they are out of it by times 5 (eg. if they were out of it by 10ft it and max damage was 140 it would be 140 - (10X5) also count the spheres as two separate spheres instead of one joint spell (even though they are)

The spell heavily damages or disintegrates everything within the radius that isn't being worn or carried and entering the flaming sphere will reduce the creatures AC by 1

* A diamond worth at least 500gp which the spell renders worthless, a vial full of blood which the spell empties, and the heart of a medium or larger creature which the spell consumes.