Azareck's Final Catastophe

Harness the destructive energy of the Far Realm, unleashing an explosion of complete entropy, the pinnacle of destructive spells. This spell was made for mass destruction and chaos, nothing more and nothing less. Many will die when someone casts this spell and they must be prepared to live with the destruction this spell will wrought: tear those mighty symbols down to infinitesimal specks to dust, watch the bodies of men, woman and children wither and die, and look on as the heavens scream an impotent scream of anguish. 

Choose one point with 10 miles that you can see or picture in your mind and fire a pitch black orb of pure entropy. This orb goes through everything, nothing can stop it as it seeks out its destination, acting as a disintegrate spell when interacting with force structures. Upon impact the target must make a Constitution saving throw, on a failure taking 40d6 Force or Necrotic damage, on a success they take half damage. if the target dies they are reduced to dust and can only resurrected via a True Resurrection or Wish spell.

From here an explosion of catastrophic energy occurs, every creature in the radius except the original must make a dexterity saving throw (ignoring the Evasion feature), on a fail they take 40d6 Force or Necrotic damage, being disintegrated if reduced to 0 hit points. 

The spell goes through corners and ignores cover. Non-magical organic structures wither and die and non-magical inorganic structures crumble to dust. The expanding sphere acts as the disintegrate spell when interacting with force structures. Life cannot grow in the effected area for the next 1000 years.