Withered heart has strong magical aura of transmutation and necromancy (detect magic reveals it as such). Its fleshy surface looks blackened with rot and pungent reddish bile seems to be dried stuck inside of its aortas. Withered Heart is considered magical object and has these properties:

• It has AC of 11 and HP of 5.
• Immunity to all damage except radiant.

A creature that has a heart in its own body can attune to the withered heart as though it were a magic item while holding it. Once attuned, the creatures own heart switches places with the Withered Heart and their original heart becomes the new Withered Heart (that new creature can attune to). Upon attuning to the Withered Heart they still gain these properties:

• Their type becomes undead, as their blood now stops circulating without a beating heart. Over short period of time, their skin becomes more pale and void of colour.
• They assume the racial features of the owner of the Withered Heart and lose all their own original racial features. However the appearance and alignment of the attuned creature does not change.
• They gain Undead Fortitude feat: The creature cannot fail death saving throws unless they have taken radiant damage that round as such they do not benefit from rolling 20 or 1 on d20 die. Taking radiant damage while being at 0 HP and unconscious, they fail their next death saving throw automatically.
• They can't benefit from any magical healing. Instead they heal the amount of necrotic damage taken.
• They are vulnerable to radiant damage.

Curse. This item is cursed. The attuned creature forms unholy bond between its body and the Withered Heart. When Withered Heart should be destroyed, the owner of the heart dies instantaneously. If new creature attunes to the Withered Heart and the original owner of the heart is still undeathly-alive, the original owner dies instantaneously. When the attuned creature or the Heart is subjected to remove curse, dispel magic (DC22) or the Heart comes into contact with antimagic field - the creature dies instantaneously. Upon death, they cannot be revived by any normal means, less than a wish.

Notes: creature with living/beating heart, Cursed