Cacophonous Cataclysm (Revised)

• As an action, you begin to cast this spell, summoning a 50ft radius circular arcane sigil above the target area within range.
• As a bonus action, you must charge the sigil by casting 6 additional ranged spells 5th level or higher, using up their corresponding spellslots in the process. You may upcast lower level spells to fit this requirement. You may cast the same spell multiple times.
• As a reaction, before the beginning of your next turn, you may release this spell. All of the spells that were used to charge the sigil take effect at the same time. All targets with a 100ft radius of the center of the arcane sigil must attempt a saving throw against each individual spell that has taken effect. If concentration is lost as a result of taking damage while this spell is charged, you lose control of the spell, the area of effect extends to a 1000ft radius and the spell is released immediately.

This is a miniature version of a spell gods cast to end civilizations. To say that the knowledge required to cast it has been lost would be inaccurate. In order for something to be lost, it has to be owned in the first place. Mortals were never meant to wield this power. Were they to learn of it, weaker, more covetous gods might even jealously strike down any unfortunate soul that dares mettle in the realm of divines.