Blade of Blood

You create a blade out of solidified blood in your hand. 

When the sword appears, you make a melee spell attack against a target of your choice within 5 feet of you. On a hit, the target takes 2d10 slashing damage and 3d10 necrotic damage. Until the spell ends, you can use a bonus action on each of your turns to attack with the sword again.

At Higher Levels. When you cast this spell using a spell slot of 8th level or higher, both the slashing and necrotic damage increases by 1d10 for each spell slot level above 7th.