tendril of the hungry dead

The touch of a shadow-wreathed tendril can siphon life force from others to heal your wounds. On a hit, the target takes 4d6 necrotic damage, and 2d4 poison, you then regain hit points equal to the amount of necrotic damage dealt. Until the spell ends, you can make the attack again on each of your turns as an bonus action. if an enemy is hit by this spell and you are at full health you may instead send the dark healing to a being within 40ft to heal them instead. 

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd.