Azareck's Eyes of Ruin

Release the destructive energies of the Far Realm to annihilate everything in your path. 

All creatures in the cone must make a Constitution saving throw or take 20d8+80 Force, Necrotic or Radiant damage and half as much damage on a success. Non-magical objects and structures automatically fail and are disintegrated, withers and dies and the spell functions as a disintegrate spell when interacting with force structures. Anything reduced to 0 hit points by this is disintegrated and can only be resurrected by a True Resurrection or Wish spell. On a failed save the creature begins to crumble to dust and takes 10 necrotic damage at the beginning of each of their turns that ignores resistance and immunity and they must make a Constitution save at the end. If it successfully saves 3 times the spell ends. If they fail 3 times the creature is disintegrated and dies, regardless of hit points.