The traveler's story is it was being hunted by a dark force. We can assume it originated closer to the center of the milky way and it made its way outwards and found temporary peace in the Sol system on far off arm of the galaxy. These are the best assumptions I can make on why each race wants it. The hive: The hive want it because it seems to be the only power that can effectively fight it seeing as we are in affected by the taken king's power, they can't have such a power rising against them, simple as that. The Fallen: The fallen seems to think that we stole the traveler from them after the traveler visited them, them powerful, then it left them and caused a collapse of the Fallen's golden age. Now I think they fight against us in hopes they can have their golden age back. The Vex: The vex for some reason don't show as much obsession over the traveler as the others but I bet they still want it. from the way the vex use their Confluxes we can assume they use a form of alchemy to make their mericals of erasing time and space work but only in the VOG, and the traveler could be their form of a philosopher stone and may be the answer to bringing their work outside of the VOG. The Cabal: seem to Care less about the traveler seeing as how they're more interested in how the vex work. As far as they're concerned the traveler has an army and all they want to do to that army is crush it. The traveler: The traveler is a being of light and ether, now where do we here those two words together? The item etheric light that gives old underpowered relic new power and light, similar to what the traveler did to the humans when it first met them. The traveler is also comprised of electroweak (a substance that is theorized to have existed shortly after the big bang) and neutronium (a substance that is thought to exist inside the core of neutron stars) which makes me think, the traveler lived since the beginning of the universe and its light may be that of a neutron star. Doesn't this make sense? Sorry if it was a little long. [spoiler]to sum up, the traveler has existed since the dawn of time an is, in essence, a neutron star.[/spoiler] Quick note: I know there is more in the cards and I'm reading through to see what I missed, expect a revision soon.