Ancient Dragon Lightning Strike

Call a powerful bolt of draconic lightning from the sky, crashing into a point within a 20 feet of you. Each creature within a 5-foot-sphere on that point makes a Dexterity saving throw, taking 9d10 Lightning damage on a failed save or half as much damage on a successful one. This spell deals double damage against young and adult dragons.

Using a Higher-Level Spell Slot. The damage increases by 1d10 for each spell slot level above 6.