User blog comment:Xilinoc/Ch. 543 - Letters/@comment-2211792-20130626143149/@comment-7488132-20130626164928

Ryuken is the last quincy (at least pureblooded quincy) in Bleach. As far as I know, Uryu is half-blooded or (75%) quincy since he's the product of a pure blooded quincy and a half blooded quincy. I personally think Ryuken simply declined to be part of this fiasco and of course, since Uryu still has beef with the Shinigami, it makes sense that Yhwach would recruit him. But of course, since we are talking about Kubo's story, maybe there's more to Uryu than what meets the eye, especially after this ceremony. From Uryu's eyes, there's a sadness brewing and there's definitely doubt since he hasn't said a single word in the chapters he's been shown with the Vandereich.