Kuja sighs. "Unfortunately, nobody knows. The Summoner tribe is all but extinct, exterminated by a man who feared them. A small handful survived, as far as I am aware, but living today there are only two. One a child, too young to remember her tribe's secrets, and the other a young woman who was raised far away from the ruins of the tribe's home. Both were skilled Summoners, but I'm afraid the underlying theory behind discovering a new Eidolon is lost forever."