Starflower
The Starflower.
A mythical herb said to be capable of healing all and any wounds. Even if a person is on the brink of death from an external injury, just one petal of a Starflower would be enough to cure them. Because a Starflower had thirty-six petals in total, that meant if you obtained one, you would essentially have thirty-six lives.
Of course, this wasn't entirely fool-proof. The Starflower could only heal physical wounds. It was ineffective against Curses, mind control, and things like that. There was, however, a different flower that was essentially the Starflower except for mental wounds - and it was called the Moonflower. But that was a story for another day.