Annihilation

Summon the true annihilating power of hell fire and force. A spherical wave of black fire and force explode from the caster. Starting slow, the wave of force and flame pick up speed exponentially fast.  All creatures within a 2-mile diameter, centered on the caster, must make a dex/con save DC [20]. A successful save takes half damage. A failed save takes full damage. Everything within the area of effect is incinerated and blown apart dealing 20d10 fire damage (fire immunity is reduced to resistance, fire resistance has no effect) and 20d10 force damage.