Technically, in what I have, it's that these five just [i]happen[/i] to fit the criteria/personality the original leaders had out of all the other descendants floating around out there, and the crystal knows it thanks to the magic it's been imbued with. But it didn't know it until it was actually needed, and it wasn't really written that it was going to happen, just that the leaders were worried that it might... so, yeah. :-)