This gem is created by a ritual of sacrifice, which requires one to willingly forfeit their life force to create the artificial heart. This infuses the gem with unnatural vitality, and when given to another, it will boost their natural constitution.

This item resembles a crystalline heart with rose gold filigree and thick red liquid stored within. To attune to this item you must hold the heart on your chest for 10 minutes, afterward the heart attaches and becomes partially enclosed within you. You may not attune to this item if your Strength, or Constitution, score(s) is 19 or higher before attunement. While this item is attached and attuned to you, your Constitution score is 19 and for every 2 years that pass, your body ages only 1 year. 

The heart has 3 charges. You may regain 1d4 expended charges after you finish a long rest by sacrificing half your remaining Hit Dice (rounded up).

Adrenaline Spike: As a bonus action, you may expend 1 charge and trigger the life energy within. You gain advantage on Strength checks and Strength saving throws, and you gain a +1 bonus to melee damage rolls. This effect lasts for 1 minute or until you are knocked unconscious.

Destructive Overcharge: On your turn, while under the effects of Adrenaline Spike, you may spend an additional charge to overcharge your body past its physical limits (no action required). Doing so gives 1d4 + you level in temporary hit points and increases the bonus damage to a +2 on melee attack rolls. Additionally, you gain advantage on the first attack roll you make each turn. This state of acute exertion is taxing on your body, after Adrenaline Spike ends, you suffer one level of exhaustion.

Biological Dependency. Once you attune to the heart, you can't remove or unattune from it as it becomes a necessary part of your well being. You may only unattune from the heart when you are targeted by a wish spell (this use of the spell counts as replicating a spell of 8th level or lower), or if your Strength score is 19 or higher for 24 continuous hours. You also have these additional proprieties while attuned:

• Fragile Balance: You have disadvantage on Constitution saves imposed by the shatter spell, and if you are targeted with the spell while unconscious, you automatically fail and suffer two death saves instead of one.
• Fatigued Vitality: When rolling Hit Dice to heal, you do not add your constitution modifier.

Notes: Set: Constitution Score, Disadvantage: Constitution Saving Throws, Exhaustion, creature who is neither a construct or undead, Buff, Cursed, Jewelry