The Infinite Storm

With a deafening roar, an opening to the plane of lightning forms 1000ft above you in the air sending down the wrath of the heavens. Leaving a vicious storm in its wake for the next hour. Each creature in a 40-foot-radius sphere centered on each point you choose must make a Dexterity saving throw. The sphere spreads around corners. A creature takes 20d6 Lightning damage and 20d6 Thunder damage on a failed save, or half as much damage on a successful one.

A creature wearing or wielding metal armor or weapons will take an extra 6d6 Lightning damage

Any creature within 300ft from a chosen point must make a constitution saving throw or be deafened for 1 hour, excluding the caster.