Cataclysm

Summon a supernova of dark energy that blasts through the ground. Gravity becomes non-existent in a hundred foot radius around you. All allies are spared, but all enemies roll 5d100 for necrotic damage. Any survivors take 20d8 in lightning damage for every round they remain in the field. Roll a CON saving throw at the end of your turn. Anything above 10 and lose 1/2 of your total hp. Anything below 10 and you die.