Mu Chen had no reason to reject Han Shan's proposal. As long as there were leads on the Undying Bird, he would take the risk to go to the Myriad Beasts Tomb, even if there was no Treasure Beast.
The main reason for him to enter the Land of the Divine Beasts, other than to train himself up, was to help Nine Nether obtain the Undying Bird's divine blood to perfect her bloodline. She could then remove the damage that had been done by the Bloodline Bond.
However, the Land of the Divine Beasts was expansive, and there were dangers everywhere. It would be difficult to search for the Undying Bird, thus Mu Chen would not give up any lead that could help him find it.
Mu Chen and Nine Nether did not hesitate to accept the collaboration with Han Shan. Ink Blade and Ink Ring were fine with it as well. They had come to the Land of the Divine Beasts in search of opportunities. Although the Myriad Beasts Tomb seemed dangerous, there were great opportunities within.
