Death Blade

You brandish the weapon used in the spell’s casting and make a melee attack with it against one creature within reach. On a hit, the target suffers the weapon attack’s normal effects, along with an extra 1d8 necrotic damage, and patches of shadow jump to different creatures of your choice that you can see within 5 feet of it. The secondary creatures each take necrotic damage equal to your spellcasting ability modifier. On a miss, the target gains 1 level of exhaustion.

Additionally, regardless of whether the attack hits or misses, the target must make a Constitution saving throw. On a failure, the target gains 1 level of exhaustion.

At higher levels.

At 5th level, the melee attack deals 2d8 necrotic damage to the target on a hit, and the necrotic damage to the surrounding creatures increases to 1d8 + your spellcasting ability modifier.

At 11th level, the melee attack deals 3d8 necrotic damage to the target on a hit, and the necrotic damage to the surrounding creatures increases to 2d8 + your spellcasting ability modifier. 

At 17th level, the melee attack deals 4d8 necrotic damage to the target on a hit, and the necrotic damage to the surrounding creatures increases to 3d8 + your spellcasting ability modifier.