Daxanathor's last stand

You become a bright streak of light that coalesces on a point within range and then explodes into a violent surge of electricity. Each creature within a 20 ft. radius sphere centered on that point must make a dexterity saving throw. A target takes 20d8 lightning damage on a failed save, or half as much damage on a successful one. You then must make a constitution saving throw with a d.c equal to the number of targets affected + 10 or die. On a successful save you fall unconscious instead.

The target has disadvantage on the saving throw if its wearing armor made of metal.

When you cast this spell using a spell slot of 8th level or higher, the damage increases by 2d8 for each slot above 7th.