Taox actually wanted Oryx and his sister's dead before they even made a pact with the worm gods. Also Savathun confronted Oryx many times, saying that she thought that what they were doing might not be right. Also Savathun desired to be a queen and a mother since before they became gods. Savathun also had a coven, when Oryx and Xivu Arath didn't. Mara Sov also has a coven. In the Gift of Mast card in the Book of Sorrows, Savathun acquired a 'secret purpose' before telling Oryx and Xivu that they should part ways. I'm thinking this purpose might have had something to do with the Awoken/ becoming an immortal mother and not needing her worm. When you consider the HoW grimoire, and how it continuously hints that Eris and Mara are kind of working together not necessarily against the tower, but in secret, it starts becoming very interesting. Especially because Mara Sov and the guardians were technically enemies before our guardian is resurrected. Basically I'm thinking Eris and Mara are Taox and Savathun. But it's all speculation. Edit: I'm thinking Mara wants the Traveler for the Awoken, not to destroy it as Oryx wanted to. This would give her a reason to fight Oryx, even if she knew her fleet would be defeated. If she did die in the fight, she would still live in her throne realm as well. But I have a feeling that there's a reason Bungie has been ambiguous about her whereabouts.