Wondrous (trinket), Very Rare (Requires Attunement)
This nightmarish necklace is a lodestone for departing souls. A fleeing spirit caught in its aura is snatched and dragged into a dark limbo. The wearer can later unleash its captured ghosts to create a gale of dark protection.
This feat comes with a price. The few accounts written of these lockets tell of owners being haunted by the spirits they’ve captured. Some see shadowy figures in the corner of their vision, others hear insistent pawing and scraping in the ground and walls.
Mechanic
As an action, you can speak a command word and call forth fiendish spirits to protect you. They swarm around you to a distance of 15 feet for 10 minutes. When you use this ability, you can designate any number of creatures you can see to be unaffected by it. When an affected creature enters the area for the first time on a turn or starts its turn there, it must make a Wisdom saving throw. On a failed save, the creature takes 6d8 necrotic damage. On a successful save, the creature takes half as much damage.
Additionally, if a creature dies inside the area, its soul is dragged into the locket of captured souls. You deal an additional 1d4 necrotic damage for each soul that is captured while you are attuned to the pendant.
After using the locket of captured souls, you must take a short rest before you can use it again.
Curse: The locket of captured souls is cursed, a fact that is only revealed when an identify spell is cast on it, or you attune to it. After attuning to it, the curse will remain even if you are no longer wearing it. You have disadvantage on perception checks, and you can only roll up to half your hit dice during a short rest.