The Shadow Legion are completely devoid of a command structure without Calus as they all were essentially lobotomised/brainwashed clones to suit his needs. The Sol Divisive aren’t directly controllable, we’ve seen their Vex nature clash with the Witness’s goals before, see the Deterministic Chaos mission. The Scorn seem to have been ‘cut loose’ to an extent after Xivu’s banishment. So, that leaves us with House Salvation, Hive and Taken. The Hive and Fallen are attacking directly while the Taken seem to be occupied with something else in this content update, as per Bungie themselves. It’s just the reactionary impulse of the Witness after Crow suddenly appeared on the other side of the portal. We’ve suddenly proven that the Pale Heart isn’t unreachable for us and so the Witness turns it’s attention back to us in order to stop us. What’s more interesting is who’s leading this assault? The House of Salvation and Hive combination suggest Xivu, especially since Eramis left Sol. But the Pyramids in the sky suggest either direct involvement from the Witness (Explains why the fleet has been silent since it entered the Traveler) or a Disciple. Whether Bungie are going to hastily introduce a new Disciple, reveal Xivu as a Disciple or just do the smart thing and use the opportunity to flesh out the Witness a bit more as an antagonist, it’s an interesting question to ponder. Of course we might know more about what the Taken are up to when they reveal this other PvE thing next stream, which should give us a better idea on the larger picture here.