According to the lore that bungie wishes to forget for some reason, she has to do something Oryx stood for. In the lore Oryx brought his sisters back by first conquering a planet, which brought back Xivu Arath or whoever, and then back stabbed her or some alien leader which brought back Savathun. Keep in mind this was after they were killed in both their throne worlds and the real world. To bring Oryx back she would have to try and understand something in the universe. Perhaps the light? By doing so the taken king would be back. Theoretically according to lore bungie isn't using anymore