"Barrier Pillars... Kisuke Urahara really is impressive."
Since he was cooperating with Aizen, Shen Fei was doing his utmost aside from guarding against Aizen turning on him after crossing the river. Aizen was probably in much the same position.
With Aizen's help, Shen Fei's plan became much simpler. Although he had learned quite a lot from Tokinada, there was still an enormous gap between him and Aizen, a Soul Reaper who had spent centuries in the Soul Society. This was especially true when it came to Kidō, where Aizen possessed extraordinary mastery.
That extraordinary mastery did not mean merely being proficient in the hundred publicly available Kidō spells. As long as one had sufficient spiritual pressure and was willing to learn, anyone who was not as dull as Renji could master them. It referred to Aizen's understanding of Kidō and his use of spirit particles.
Kidō was, in essence, the manipulation of spirit particles. Just as ninjutsu required Chakra, changing a small part of it was enough to develop a completely different ability.
For example, Hakufuku, the Kidō that could put people to sleep for a period of time, was a combined application of binding and destructive spells. Then there was the Mirror Gate used by Toshiro Hitsugaya, an advanced barrier capable of reflecting external attacks. Hitsugaya had used it while protecting Momo Hinamori, though the Mirror Gate could not defend against attacks originating from within.
Thanks to Aizen's insights into Kidō, Shen Fei altered his previous plan. He recalled how Kisuke Urahara would later transfer Karakura Town to the Soul Society, as well as Tokinada's plan to use the Barrier Pillars to move the Spirit King Palace, and that reminded him of the Barrier Pillars' function.
Making the three sides fight was simple enough on Hueco Mundo's side; all