Blade of Blood

You create a blade out of your own blood to use as a weapon. The blade is similar in size and shape to a scimitar, and it lasts for the duration. If you let go of the blade, it disappears, but you can evoke it again as a Bonus Action.

Whenever you cast this spell you take 1d4 damage

As a Magic action, you can make a melee spell attack with the bloody blade. On a hit, the target takes Necrotic damage equal to 3d6 plus your spellcasting ability modifier.

Using a Higher-Level Spell Slot. The damage increases by 1d6 for each spell slot level above 2.