Whups. Left out the key words again...
"Ignore all damage that would kill you this turn."
That make it more clear? This would still just mean that your hp cannot drop below 1 for that turn. It WOULD decrease to a minimum of 1 though, making early play completely useless. If this better conveys the right idea than "You cannot be defeated by damage this turn." I can always change it.
But I simply do not understand why there is a need for extra damage. If you use the card and it actually prevents death, you'll have 1 hp. Almost ANYTHING can deal 1 damage in most circumstances. If it doesn't actually prevent death, then it was a wasted card. And if using this card allows you to draw a life saving card, the card itself wasn't necessary. There are other cards that would be more effective; Hourglass or Precognition for example. Or you could simply have drawn the life saving card instead of this one because this isn't in your deck. Even if this DID force damage on you the next turn, you could still chain them and simply ignore the damage that was intended to kill you. Therefore preventing a chain isn't even a valid reason.
Perhaps I'm just stupid, but I don't understand where you're coming from. Maybe you can't grasp this card thematically and you need the drawback to fit it into your realm of possibility. I don't know. But whatever it is, I can't see it. I like it the way it is, aside from some minor wording issues, and plan on keeping it this way unless I see a reasonable argument otherwise.