Surging Lightning Bolt

You Must have Lighting Bolt prepared and on your spell list to prepare or cast this spell.

A stroke of lightning forming a line 150 feet long and 5 feet wide blasts out from you in a direction you choose gaining power from every target it hits. Each creature in the line must make a Dexterity saving throw. A creature takes 8d6+1d6 for every creature in between it and the caster that have been forced to make a save. that 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 4th level or higher, the damage increases by 1d6 for each slot level above 3rd.

This technique was developed by the Archmages of Volitaris and may not have been developed in other lands. Check with your DM whether it exists in your world.