Umbilical of life and death

A beam of green energy lances toward a creature within range, forming a sustained connection between you and the target. Make a ranged spell attack against it. On a hit, the target takes 2d6 necrotic damage, You regain half the hit point equal to the damage

On each of your subsequent turns, you can take a Bonus Action to deal 2d6 necrotic damage to the target automatically. You regain half the hit point equal to the damage. 

The target can't regain hit points and any hit points the target would regain while link transfers to you

The spell ends if the target is ever outside the spell’s range or if it has Total Cover from you.

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