A dark-purple heart steadily beats inside this small hardwood chest. All creatures within 60 feet of the box can hear a quiet heartbeat, and feel the rhythmic thump deep within them.
As an action you can point at a creature you can see within 60 feet and force them to make a DC 12 Constitution saving throw as they feel a tremor in their heart. On a failure they take 3d6 Necrotic damage and their hit point maximum is reduced by an amount equal to the damage dealt. On a success they take half as much damage and their hit points are not reduced. This reduction lasts until the creature finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.
A creature with no heart automatically succeeds this saving throw.
If you are killed while attuned with this heart you are brought back to life at the next dawn as if by the spell
Curse. Each time you use the feature Mortal’s Fragility if you have a heart and are not undead you must also make the saving throw against taking necrotic damage, though your hit point maximum is not reduced.
Additionally, if you are resurrected by the Immortal’s Resistance feature you are now considered undead and have the Sunlight Sensitivity feature: while in sunlight, you have disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.