Your Constitution score is 19 while you wear this amulet and it has its charge . It has no effect on you if your Constitution is already 19 or higher without it.

also grants Relentless Endurance. When you are reduced to 0 hit points but not killed outright, you can drop to 1 hit point instead. once the charge is expended, it can only be recharged via a repeat of the ritual in which it was created. 

ritual: requires a High level Paladin or Cleric, an Artificer of expert talent,  a golden bowl or goblet and a gelatin substance from a secret recipe that can hold momentarily the holy power, long enough to bind to the amulet and fill the crystal.

Notes: Set: Constitution Score, Item binds to user once put around their neck, cannot be given to another once it has been bound, Buff, Jewelry