You prick your finger and smear your blood on the weapon used in the spell’s casting then make a melee attack with it against one creature within the weapon’s reach. On a hit, the target suffers the attack's normal effects, and takes extra necrotic damage equal to your spellcasting ability modifier.   At higher levels. The spell’s damage increases by 1d8 when you reach 5th level (1d8 + modifier), 11th level (2d8 + modifier), and 17th level (3d8 + modifier)