Allister's Righteous Explosion

You crush a vial of your blood in your hands. You then begin your incantation, invoking the rights of arcana that make up the very essence of your being. Unleashing a column of destructive fire that expands out in a radius of 100 feet, and 200 feet tall of all different colors centered on a point in range of your choice. Creatures within the range must make a Dexterity Saving Throw taking 20d10 fire damage on a failed save or half on a successful one.

Casting this spell causes the area of the explosion to be set on fire doing an additional 1d8 of fire damage to all creatures that try to pass through it. Any creature that ends their turn within the area takes another 1d8 fire damage at the start of their next turn, and continues to take damage until they leave the area.   

At Higher Levels. When you cast this spell using a spell slot of 8th level or higher, the damage increases by 5d10 for each slot level above 7th.