Board Thread:Questions and Answers/@comment-31283382-20131221170348/@comment-1268838-20131221213209

Nimaiya in Chapter 540: "I'm saying this Hollow... is your Zanpakutou, simple as that. The Hollow that Aizen created - he called it "White" - was formed from the souls of many Shinigami. And ironically enough... That's pretty much the same as how my Asauchi are created."