Apocalypse Now

Description: You call down an unimaginable force of destructive energy upon a point you can see within range. A blinding flash erupts, followed by an inferno of fire, a wave of corrosive energy, and a colossal shockwave that shatters the very air.

Initial Blast:

Creatures within a 200-foot-radius sphere centered on the chosen point must make a Dexterity saving throw. On a failed save, a creature takes 20d6 radiant damage, 20d6 fire damage, and 10d6 acid damage. On a successful save, a creature takes half as much damage.

Blinding Flash:

All creatures within the 200-foot-radius sphere are automatically blinded. At the end of their next turn, an affected creature can make a Constitution saving throw. On a successful save, the blindness ends. On a failed save, the blindness persists until the end of its next turn, at which point it can attempt the saving throw again.

Concussive Shockwave:

Creatures within a 500-foot-radius sphere (but outside the 200-foot-radius initial blast) centered on the chosen point must make a Constitution saving throw. On a failed save, a creature takes 10d6 thunder damage, is knocked prone, is deafened for 1 minute, and its movement speed is halved for 1 minute. On a successful save, a creature takes half as much thunder damage and is not subjected to the other effects.

Radiation Field:

The entire 1-mile radius sphere originating from the point you chose for the initial blast becomes a "Radiation Field" that persists for 1 hour. This area is considered heavily obscured.

Initial Exposure: When a creature enters the Radiation Field for the first time on a turn or starts its turn there, it takes 5d6 acid damage. This damage is not subject to a saving throw.

Radiation Sickness: Any creature that takes damage from the Radiation Field must succeed on a Constitution saving throw or gain one level of exhaustion. This exhaustion can only be removed by a Greater Restoration spell or similar magic, or by spending 24 hours outside of any radiation field. This exhaustion is not cumulative with other forms of exhaustion for the purpose of the 6th level of exhaustion rule.

Persistent Radiation: Even after leaving the 1-mile radius, creatures that took damage from the Radiation Field are subject to further effects. For the next 24 hours, if a creature that took damage from the Radiation Field fails a Constitution saving throw against any effect, it takes an additional 2d6 acid damage.

Devastation: 

Structures and unprotected objects in the 200-foot-radius initial blast area are automatically destroyed or heavily damaged. The ground in the 1-mile Radiation Field is irradiated and tainted, hindering plant growth and making water undrinkable.