A medically perfect miniature replica of a heart. It feels cold at first but as you hold it it seems to warm up and begins to beat in synchronization with your own heart. The charm is a perfectly made replica of a humanoid's heart except for a hairline crack that bisects it. Pulling at both halves reveals that it splits in two. If shared with another individual the half that you keep will beat in time with the heart of the individual that has the other side and their half beats in time with your heart.
While attuned to this object you feel when the other user is harmed and you can choose to take the damage instead causing the injury to appear on your body. This damage that you choose to take ignores any resistances or immunities that would otherwise affect how you receive the damage. Additionally when you are healed through magical means you can choose to channel that healing magic through the heart charm and into the other user causing them to receive the healing.
When one user is knocked unconscious and begins to make death saving throws then the user who is still up will suffer a point of exhaustion for every failed death save. If two people are attuned to this item and one of them dies then the user who is still alive will immediately go unconscious and begin to make death saving throws. If one user dies while the other is already unconscious then the unconscious user will also die on their next turn regardless of how many death saves they have failed or succeeded.
If a single user is attuned to both halves they will take extra damage and receive extra healing when they are healed magically. This extra damage and extra healing equates to 1d4 per single instance of receiving damage or healing.