Lex had once sealed his memory of Wu Kong's name from within the Chamber of Secrets, but upon reading it again, suddenly those memories returned to him, once again reminding him of how dangerous his interactions with this particular guest were.
He had to be in complete control over his thoughts, lest his thoughts be seen by the guest. The worst part was, he wasn't sure if the Host Attire would protect him from the guests gaze, for the system seemed entirely incapable of detecting this particular guest at all. It was uncanny.
But it provided Lex with a proper justification to meet with this particular guest, which was convenient because he had already decided to meet him. If there were potentially other Dao Lords hunting this guest, then it would be inconvenient to keep him here for a long time.