Crimson Lightning Bolt

Black blade spell.

Can be used without a level 9 spell, but you must be a level 3 druid to use it once. 5 to use twice. 7 to use three. 9 to use four times. if of course you haven't used up your sword charges details of the capacity of the sword spell in its description

A stroke of Crimson lightning forming a line 100 feet long and 5 feet wide blasts out from you in a direction you choose. Each creature in the line must make a Dexterity saving throw. A creature takes 8d8 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.