Eldritch Cannon: Infernal Overcharge

Charging up your Eldritch Cannon, you fire with a thundering roar that can be heard for miles. A fiery yellow streak races across the skies and strikes with a deafening crack that shakes the earth itself. 

When cast, the caster rolls a d20 Intelligence (Arcana) check

• On a natural 1, the spell fails catastrophically. Each creature within a 10 foot radius must do a d20 Dexterity saving throw. Any creatures within the blast radius take 16d6 fire damage on a failed save, or half as much on a successful one. Everything flammable within a 20 foot radius ignites, doing d8 fire damage.
• On a 2-7, the spell misses the target by at most 10 feet to the left, right or behind the target.
• On a 8-12, the spell lands 10 feet in front of the target.
• On a 13 or higher, the spell manages a direct hit.
• On a natural 20, the spell does a critical hit, dealing twice as much damage.

On detonation, everything within 5 feet of the detonation point takes 16d6 fire damage and must roll a d20 strength check with a disadvantage. On a failed save the target is knocked back 15 feet, and on a successful save 5 feet. Everything flammable in a cone 60 feet long and 10 feet wide behind the detonation point catches on fire, and any creatures within that area take d8 fire damage. Stone or metal in the 5 foot area of detonation or less than 10 feet behind the detonation will be molten.

If the caster is distracted during the spell casting time, the spell fails. If the spell leaves the target with -10 health or less, the target's body and all items on it are turned to ash. The casting of this spell leaves the infernal cannon unusable for 1 day and cannot be cast again for 3 days.