Vampire Bite

Your blood-thirsty bite can siphon life force from others to heal your wounds. Make a melee spell attack against a creature within your reach. On a hit, the target takes 2d4 necrotic damage, and you regain hit points equal to half the amount of necrotic damage dealt. 

Cantrip Upgrade.  The damage increases by 2d4 when you reach levels 5 (4d4), 11 (6d4), and 17 (8d4).