[quote=BB]
You can still save Stein, but you clearly need to get him out of there now. I wouldn't suggest fighting while you can do that.Like I said, is it "Steins" heart?
[/quote]

yes. It belongs to him, it is his one and only original heart. He had it removed earlier to counter fragarach, replaced with a mechanical heart. Of course, aqua vitea had caused his heart to grow back, but that meant there were two hearts which were his, and he used his original heart to block the heart by holding it in front of him.