I believe the Vex stand apart from the Traveler. I believe the Hive were the First People that encountered The Traveler, and the Traveler's Light could not penetrate their society and they were left to become the hollow, undead husks that we know, empty of Light and hope. The Fallen were The Traveler's favored people for a time, and as their name suggests, they fell from The Traveler's grace and lost the Light, but they had grown dependent on the Light. Replacing it with Ether, a poor but necessary substitute, The Fallen now pursue The Traveler to take vengeance, or to take what they think they are owed. The Cabal, like the Vex, stand apart. They're likely not even part of the Darkness, but another deep space-faring civilization that encountered The Traveler and The Darkness, and are now embroiled in an ages-long fight with them both.