Board Thread:General Discussion/@comment-25252005-20140801095943/@comment-8986886-20140803023519

VinnyLam wrote: Wouldn't he need to have a reiryoku twice as high as a Shinigami captain in order to tap into its power? Something that Aizen had.

In which case, it would be useless to him.

No, Aizen only required that amount of Reiatsu to use the Hogyoku when it was still in hibernation. That's why Aizen's plan was delayed several months, and the Shinigami had time to build Fake Karakura Town. Afaik, there are no conditions for using the Hogyoku when it's fully awake, except that any wishes made are limited by its master's potential, meaning it can't make the 'impossible' happen; like bring the dead back to life.

The only prequisite is that the Hogyoku must recognize the owner as its "master", which was evident when the Hogyoku healed Aizen even after Gin had stolen it from him. Kisuke later confirmed it when Aizen was losing his powers at the end. It's possible that Kisuke's words were intended to make Aizen further doubt his own influence over the Hogyoku, to the point where it wouldn't recognize him as its master anymore.

In this scenario the Hogyoku would work similar to Gremmy's power of imagination, which only worked as long as he never doubted it. Another analogy would be that of the king and his horse, which was evident between Ichigo and his inner Hollow, where the power that is being used will challenge its master if they show any signs of weakness.