Ashes to Ashes

You ignite yourself with an immense, fiery explosion that deals devastating damage to all creatures around you, including yourself. As you concentrate on this spell, you cannot take actions, or reactions, and you may not willingly interrupt your concentration on this spell. If your concentration is broken, the spell does not take effect, but the spell slot is used and the material components are consumed. This spell's effect occurs at the start of your next turn so long as your concentration is not broken; causing you to take 300 points of fire damage. This spell ignores both resistance and immunity to fire damage. 

All creatures within 100 feet of you must succeed on a Constitution saving throw, taking 25d10 fire damage on a failed save or half on a successful save. Additionally, creatures closer to the caster when this spell is cast takes more damage depending on their proximity.

• Creatures within 100 feet take an additional 25 damage
• Creatures within 50 feet take an additional 50 fire damage
• Creatures within 25 feet take an additional 75 fire damage
• Creatures within 10 feet immediately fail their saving throw and take an additional 100 fire damage

Creatures that took 100 fire damage or more from this spell are Blinded and can only be healed by a Greater Restoration or Heal spell. Any creature reduced to 0 hit points by this spell is turned to ashes and may only be brought back by a Wish spell. However, the determination of a Wish spell's success will ultimately be left to the discretion of the game master, and input from the player character. The successful casting of this spell will result in the caster never being able to cast it again.