Checkmate.

What just happened is one of the sage's plans. He would have gotten what he wanted either way which is to win the bet. He allowed the serpentine world to change the last boss of Arena 28 so that he will have to input his own law of order into the arena since he wasn't the one that created the arena. It will give Soverick the chance to get a hold of it if he manages to defeat it. He had faith in Soverick to at least be able to match the absolute domain and defeat the Viper.

Then the first sage gave his co-administrator the chance to revert the changes in exchange for him changing the last boss of the arenas under the control of the serpentine world god. The sage would have done something far stronger than the absolute domain. If even Soverick had to resort to using such a powerful move to kill the last boss, then the race of the serpentine world god will never be able to acquire the keys needed to unlock the next designation after Emperor.