Soulstring Amulet

This amulet features a pendant resembling a twisted, darkened crystal encased in metal that glimmers like bone. While wearing the Soulstring Amulet, you gain advantage on saving throws against being frightened. Additionally, its necrotic energies allow you to recover a number of hit points equal to your proficiency bonus once per long rest when you kill a creature. However, when you use this ability, the amulet siphons a piece of your own life essence. You take necrotic damage equal to your proficiency bonus. If you use this feature more than once per long rest, the necrotic damage increases by 1 for each consecutive use, potentially exhausting you.