After reading the whole book. I believe that eris at the end of the story is talking to one of Oryx's sisters, because they always are trying to kill each other. I believe that the smart sister had eris help the light to defeat him so she can step in and take power. If you have read the book you know that oryx and his sisters split up to each gain power, because there presences were holding each other back. Oryx even says that he is worried about his siblings, stating that they may even have surpassed him in power. Keeping all of this in mind I believe that eris is a traitor, but is working against oryx so that a different hive ruler can take over. So as she says "my queen" she is not talking to Mara sov, but one of Oryx's sisters. Thought?