Demon Blade

Channeling fiendish energy from abyss, you raise your hand and cut down with a blade made of necrotic energy, damaging any creature in a straight line out to 60 feet. The energy blade is 5 feet wide. Each creature in the line makes a Dexterity saving throw, taking 3d8 necrotic damage on a failed save or half as much damage on a successful one. 

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d8 for every slot level above 2nd.