Every type of star beast has its limit of transformation. Take the stubborn donkey, for instance: according to conventional logic, the peak of the sixth rank is its limit. Afterward, no matter how much it devours the power of star sources, it can only stop at the peak of the sixth rank. As for those ancient exotic species, they can reach the seventh, eighth, or even ninth rank, or perhaps transform to the extreme.
Mo Yang's idea was not entirely impossible. The Star Domain contained countless rare treasures and natural herbs; if some heaven-defying medicinal pills were refined, helping the stubborn donkey transform would not be difficult at all.
At least for him, it was not difficult.
Chapter 687