Apocalypse from the sky

Apocalypse from the sky was a corrupt spell that could only be used for mass destruction.

Effects
The spell caused massive amounts of acid, fire, or concussive force, the caster's choice, to rain down within a certain radius around the caster. This radius encompassed ten miles (16 kilometers) at minimum and increased in ten-mile increments with the caster's skill.

The amount of destruction this spell caused could result in the extinction of an entire population.

The caster was not safe from this spell.

Components
This spell required somatic, verbal, and material components and incurred a corruption cost. The material component was an artifact. When this spell was cast, one dedicated to the cosmic force of good was usually used to fuel the spell, which was considered an act of perversion. The spell's corruption cost was unique, as just preparing it was dangerous to the caster's sanity. Actually casting it drove the caster insane while also wracking his or her body.

Casting the spell took an entire day.

History
Caira Xasten once tried to eradicate Waterdeep in order to draw Atropus to Toril to end the world. The artifact she intended to fuel the apocalypse from the sky spell was the  Book of Vile Darkness.