Theories: *The Vex don't come from the future, but the past. They were created as a servitor race in the Hive's distant past (Notice the shape of the limbs and the crests, though the number of fingers is off), before the Hive's quest for immortality tainted them completely. Possibly still operating on ancient guidelines for conquest, and also possibly do not recognise the modern day Hive as their original masters. *The Hive possibly also created the Traveller (or Travellers) as sentient terraforming engines to create habitable worlds and advance indigenous races, at first benevolently, but as the Hive's hubris and evil grew the newly indoctrinated species were used as slave races. *The Fallen were one of the last (or first) species to be found and changed by a Traveller, only to fight back, but be destroyed/scattered when the Hive came to claim them (they worship mini-travellers). Some factions of Fallen have allied themselves with Humanity, or at least Awoken (Queen of the Reef has Fallen Bodyguards if I interpreted one of those trailers correctly), but others still blindly seek the favour of the Traveller on earth, believing it to be their saviour, and Humanity its jailor. *OR: The Fallen created the Traveller as a Terraforming engine, and truly believe our solar system is theirs because they found it and made it the way it is. *I have no idea where the Cabal fit in to any of this. Although the acute physiological differences between the "soldiers" and the "workers" (with no hint of a hive mind like the Hive, and possibly the Vex) says purpose engineered gene-pools to me, tenuously linking them to the Traveller as well. *The Hive itself is not the Darkness, although Crota may be one of its chief agents. I really have no idea, and all of the above was cobbled out of thin air.