Yeah the Crystal Ter'Angreal in Rhuidean. That would have been pretty cool to foreshadow it that way. For example "The Jenn Aiel died out during the War of Power before they could find a solution to the Balefire problem". That would show that it definitely WASN'T just pulled out of someones ass last minute (which we will never know) and it would be a nice little "aha" moment for readers. As it stands if Jordan had it in there since Eye of the World then his foreshadowing certainly is crummy as things like that should be subtle and in there from the very start. I mean, Balefire is such a big deal to the ending of the book and he knew the ending before he started writing, right?