Broken Base: The revelation Royce is the heir of Novron. Many believe Hadrian would have made a better choice.
Covers Always Lie: The Orbit covers typically depict Royce and Hadrian as being of comparable heights, while in the books Hadrian is much taller. For some reason, Royce always wears a stalwart expression while Hadrian is scowling. Hadrian rarely scowls in the books; that's Royce's job.
Moral Event Horizon: Regent Saldur is a Affably Evil manipulative corrupt but hilarious Evil Chancellor who unwittingly sets up Thrace to be Empress. He is seemingly more buffoonish than dangerous right up until the time he manages to capture Arista. He then tells her he's going to have her repeatedly raped and tortured unless she gives him the name of her co-conspirators in the palace. She gives him the name of an unrelated employee who is promptly killed.
Arcadius passes this when we find out he murdered Gwen, a woman he raised as his own daughter, in order to hide the existence of Royce's daughter Mercy from him.
Royce passes this when he murders three innocent guards while kidnapping Modina and Saldur. He is eventually forgiven for the kidnapping but no one mentions the murdered guards, who were good guys who were just doing their jobs.