Blast of the Living Artillery

For the first two actions the caster surrounds themself in a swirling sphere of fire. The way that each individual does this is unique, but they surround themselves in an exceptionally large amount of fire. On the third action, the caster blasts the fire that they have conjured to a point that they can see. If the blast travels more than 500 feet, it will begin to lose its potency. After 5000 feet of travel, the blast will burn out completely. 

When the blast makes impact, it deals 10d10 fire damage to anything within 10 feet of the impact. Anything within a 20 foot circle outside of the impact make a Dex check (DC 16). On a failed check, they take 7d10 fire damage, or half as much on a successful save. For another 20 foot radius outside of that, all creatures must make a Dex check (DC13). On a failed save, these creatures take 5d10 fire damage, or half as much on a successful save. The blast also has a physical impact that can smash walls and knock back anyone who does not succeed a strength check. Anyone within 10 feet of the impact automatically fails the check. 

After 500 feet, the strength of the blast diminishes by 1d10. Each additional 500 feet of travel takes away another d10 from the damage. At 3000 feet, the outer circles of damage are taken away, and the creatures at the center make a Dex check (DC 12) to take the damage. At 3500 feet, the physical impact of the spell is lost.