Locket of Charm (5e Equipment)
From D&D Wiki
Wondrous item, rare
This locket appears to be of fine elvish work with filigree leaves and flowers all over. It cannot be opened except by an attuned wearer. Once attuned, the wearer can open the locket to charm any creature within 30 feet who can see or hear them and lasts for one hour or until the wearer closes the locket. This can only be done once per day, resetting after a long rest. Creatures can make a wisdom save DC17 to resist the effects and those immune to charm will be unaffected.
Curse: After closing the locket, the wearer must make a charisma save DC17 or have their HP max reduced by the number of creatures affected by the locket's charm. To restore the HP max, the wearer must un-attune, then if their HP max is above 10, it can be restored by a lesser restoration spell. If the wearer's HP max falls below 10, it can be restored by using both the remove curse spell and a restoration spell.