A flash of lightning forming a line of 40 feet long and 5 feet wide blasts out from your staff in a direction of choice. Each creature in this area needs to make a Dexterity (DEX) saving throw. On a fail, it takes 4d10 necrotic damage on a failed save or half as much on a succesfull save. 

The lightning ignites flammable objects in the area that aren't being worn or carried.