He needed to use his words to guide Mu Cheng through channeling the profound esoteric skill. If all went smoothly, she would remain completely unconscious throughout the entire process—essentially acting as a human puppet—because all her focus would be hyper-fixated on the sword.
This required her to have absolute trust in Su Yue. The hypnosis practiced in the Divine Land in the past actually shared a similar underlying principle. If she successfully refined the Creation Sword, she wouldn't even be aware of the process; it would merely feel as though she had a long dream.
This was an unorthodox method. If one wanted to seriously study combat tactics, such a shortcut was strictly forbidden. Furthermore, it wasn't easy by any means.
First of all, the demands placed on Su Yue were exceptionally high. Under normal circumstances, this was a way for elders to help their juniors cheat. However, Su Yue was a freak of nature, which was the only reason he dared to attempt it.
