Ancient Dragon's Lightning Strike

Raising your hands to the heavens, you call down crimson lightning in a 20ft radius, 30ft high cylinder around you. All creatures besides you within that area must succeed on a Dexterity saving throw, or take 4d10 lightning damage.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the lightning damage increases by 1d10 for each slot level above 3rd.