Symbiosis

You tap into the malevolent powers of necromancy to create a dark tether between yourself and a creature within range. As you cast the spell, you harness a dark gemstone as the spells focus.

The target must make a Wisdom saving throw. On a failed save, its life force becomes linked to yours. For the duration, you gain advantage on all saving throws and ability checks against the target while they are afflicted. Additionally, whenever the target takes damage, you regain hit points equal to half the damage taken by the target (rounded down).

The cruel tether not only grants you power but also causes the target to suffer. It takes an additional 1d6 necrotic damage at the start of each of its turns for the duration of the spell. The target can make a Wisdom saving throw at the end of each of its turns, ending the spell on a success. Furthermore, while under the effect of the spell, the target's attempts to move outside the range of the spell are futile, as if an invisible force pulls it back towards you. The target can still take actions and perform other activities within the spell's range but is unable to leave it voluntarily.