After analysing the Grimoire and ingame elements several times, here is my theory about the Darkness and the Nine. 2 of the Nine are the first Awoken who chose to do so to survive, further evidenced by Xur's statements. One of them is a Warmind who permitted them to survive the Collapse. Seeing how Cayde-6 maybe is Rasputin, it is possible the Exo Stranger miight be it, although that may also be wrong since she wants to destroy the Black Heart. So it might just be the reason why Warsats are launched at our face. One is a Ghost, which makes sense since a Darkness allied Ghost-Flower inside the Black Garden tried to make Pujari realise he was a dead-husk allied to the Traveler, a dead thing. It is similar to the message given to the Future War Cult representative by the Darkness, also seen in the memories of a dead Ghost in a more detailed explanation. I believe it is possible the Black Heart might be this Ghost-Flower. One is said to be the aspect of the Darkness itself, which is most likely Oryx by looking the description of the Eye of Oryx along with his Urn of Sacrifice being sold by Xur. As for the other 4, they are unknown entities. But since Toland says that there are 4 other Hive gods other than Crota (Eir, Ur, Xol and Yul), I believe they are these entities.