The irony of Marius's whole "I am so devoted to you I would do terrible things are your command" thing about Eric is that Marius tortured himself about that willingness to put Eric before everything and Eric finds the notion of Marius surrendering his own sense of moral judgement over to any evil Eric could come up with horrifying, but the underlying truth is Marius is only so devoted because Eric is so very much not a person who would ask him to do terrible things, the 'worst' Eric thing Eric asked of him was to kill the King which challenged Marius to re-examine his rules-focused moral framework but was not bad by most people's definitions considering the harm Octavius was doing by that point, if Eric weren't such a good person I don't think Marius would have developed the same devotion, so they're both just agonised by this willingness to do terrible things that exists only because such a request would never come.
