Twin Dragon Lightning

Two strokes of lightning forming two lines that is 120 feet long and 5 feet wide instantly strikes out from your fingers in a direction you choose. Each creature in the line must make a Dexterity saving throw. A creature takes 6d10+10 lightning damage on a failed save, or half as much damage on a successful one.
The lightning ignites flammable objects in the area that aren't being worn or carried.

At Higher Levels. When you cast this spell using a spell slot of 7th level or higher, the damage increases by 1d10 for each slot level above 6th.