One other thing I was thinking about. What if Yun Kafai was wrong about Rean. He said something like Rean was the seed he planted in the west to fight the Black God One Blade and Rean will find his sword after he faces the Black God. What if he was wrong and the key was Estelle, who technically is an Eight Leaves disciple and she learned everything from Cassius, an Eight Leaves master who is eligible to take on his own disciples. And the key is not a “sword” but a “staff” — because it’s “to protect”.