I am a DM running Tomb of Annihilation. I am toying with the idea of giving one of my level 5 players an item that prevents death, just once, and then breaks. Note that I do not mean dropping to 0 hit points, but rather actually dying. This is different from death ward. In other words, if the player is to die instantaneously through some mishap or fails his death saves, this item will prevent them from dying just that once.
I like the idea of doing this because an item that gives death ward once would break as soon as the player is about to be knocked unconscious or hit 0 HP for any reason, which isn't very infrequent. I think this item is particularly interesting in this campaign.
How powerful would an item like this be? I'd like it to be comparable to a +2 weapon or a +2 armor, or a Necklace of Prayer Beads, or a Gem of Seeing.
I have not thought through whether the item would bring the person to 1HP or stable at 0HP. I'm leaning towards the later, but I wouldn't mind hearing people's thoughts on either option.