The Emperor seems to be kind of a contingent character -- how he behaves depends on how the main character behaves, so completely that if the main character trusts the Emperor, then the Emperor seems retroactively to have always been trustworthy - in particular, rather than betray the main character and control the elder brain, the Emperor is good to his word and allows the main character to assume as much power as desired and to decide whether or not to destroy the brain. On the other hand, if the main character continually distrusts or insults the Emperor, then the Emperor seems retroactively to have always been untrustworthy. In other words, whether the main character trusts or distrust the Emperor, the story changes so that the main character's instincts are ultimately proven correct.