Desert Power

You create a sand/firestorm hybrid at a point you can see within range. The firestorm has a radius of 20ft. and extends 30ft. into the air in a cylindrical shape. All targets within the radius must make a COS (spell save DC) saving throw. On a failed save, they take 2d8 bludgeoning and 4d6 fire damage, half as much on a successful save. If a target starts their turn in the storm, they take 1d8 bludgeoning and 2d6 fire damage. Additionally, all targets inside the storm have their movement cut in half (difficult terrain), suffer from the deafened effect and can't see further than 15ft. in front of them in a cone. Targets outside the storm cannot make out the forms of creatures inside unless they use a perception check to do so. As a bonus action on their turn, the caster can expand the radius of the storm in exchange for a reduction in damage. Extending the storm by 20ft. reduces the damage to 1d4 bludgeoning and 1d6 fire (1d8 bludgeoning and 2d6 fire if used during initial casting period) and extending the storm by 40ft. yields no damaging effects (conditions still apply). 

When used at higher levels, the damage increase by an extra 2d6 fire.