Consider for a moment. You're fresh from the grave as they say. No memory of who you are, of what you are. Who do you listen to? Your Ghost. The Lucent Hive, they're not resurrected with their memories or hatred of Humanity intact. They no longer have worms to feed, worms to direct them. So who tells them how to be Hive? Other Hive, who are still listening to their worms, who still hate Humanity. Who tells them to seek out other Hive? Their Ghosts. It began with Savathun. She was dead. DEAD dead. Her Ghost, Immaru, found her corpse, basically on the outskirts of the Last City. Immaru brought her back. IMMARU directed her away from the Last City, away from the Traveler, away from Guardians. Savathun could have been a bridge between the two species, humanity and the Hive. She had no memories of who she was, no memories of her schemes, her plans. She didn't even know her name. Immaru had other ideas... Why? Because Immaru is a bitter little -blam!- who was resentful over how long he spent looking for a Guardian. He basically said, "To hell with humanity," and set the entire story in motion. From that one choice, everything else is derived. Other Ghosts turning to the Hive. The Hive proper continuing Savathun's plans from when she was alive to take the Light. Hell, Savathun said it herself, how it would have been so clever of the Traveler to just let her die; it would have been far more clever to send her a Ghost that would have made her an ally of humanity, as was done with Uldren Sov. Instead, she got Immaru. Wait and see. Immaru will be back, probably as a Disciple of the Witness, but definitely as some sort of big bad. He'll be some sort of "uber" Ghost, larger, able to resurrect the entire arena at once in whatever event we face him in. His DPS phase will probably be when his shell is open as he's standing by to resurrect all the enemies the fireteam just killed. Savathun had schemes, but in the end, she was just a tool for her Ghost.