Ancient Dragon's Lightning Strike

You summon bolts of red lightning that scatter and spread in a 30-foot radius around you. Each creature in the area that you choose must make a Dexterity saving throw. A creature takes 6d6 lightning damage on a failed save, or half as much on a successful one.
At Higher Levels.
When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd.