The Yellow Emperor obviously didn't expect to be deceived.
Even Nuwa and Chang Yi didn't realize that from the beginning, the Mysterious Woman was in disguise and concealing herself, participating with Ye Fan and Xi He in this "conspiracy." By the time the Yellow Emperor realized it, the Mysterious Woman's cultivation was nearly restored, almost comparable to that of Xi He and Ye Fan. Killing Ye Fan was pretty much impossible by then.
"Mysterious Woman, I didn't think you would disguise yourself with an ordinary human!" the Yellow Emperor said angrily.
The Mysterious Woman replied coldly, "To make you appear, using some special methods was unavoidable..."
As she spoke, Su Nu also appeared beside Ye Fan, which meant that Ye Fan now had the support of three ancient cultivators, allowing them to simultaneously fight the Yellow Emperor with the power of four.
