It is the only item in game that can be actually lost. Prior to patch 2.1, it could also have the Movement Speed bonus, which is normally not allowed on an amulet.
The unique affix is only triggered when all other life-saving effects (skills and others) fail. Remember that once it saves the character, they will be left severely weakened due to having no amulet equipped.
This is one of the few Legendary items in game that cannot be extracted into Kanai's Cube.
Stats (Level 31)Edit
"This unique amulet was originally found on a dead necromancer before being brought to Khalim, the Que-Hegan. It was he who named it, after his archbishops and their philosophers finally divined its powers. I often wonder why Khalim did not use it himself when he was mortally wounded, before being dismembered by his corrupted High Council." —Abd al-Hazir