Board Thread:Questions and Answers/@comment-10797017-20130627100621/@comment-6007020-20140530010528

Look at the article for the Hogyoku, and you'll see that I'm correct. Before Kisuke even thought up the idea of one, Aizen had created his Hogyoku. He presented his creation to the souls of hundreds of Shinigami and Soul Society residents, and it was still incomplete, until he stole Kisuke's and fed it to his. Kisuke never used his Hogyoku beyond stabilizing the Vizards souls, while Aizen got pretty busy with his, incomplete and complete.