Everyone has there own little input on why the traveler is helping the humans in this war with the darkness. first of all you may disagree with me, but the black garden that your player is looking for is with in the traveler. I believe this because the ghost could not detect your location yet the queen's brother said "Everyone knows where it is". Your player not knowing because he just came back from the dead having no idea where or what it is. The traveler is running from the darkness because it did the same for them as it is doing for the humans but the alien race that it was helping to defend it ended up trying to extract the energy for themselves. As the vex was doing in the black garden and the hive was doing on the moon, And is probably the reason why the hive have a piece of shard from the traveler. And the effects that made the Awoken was the effects of one of the former Defenders of the traveler actually using the power of the traveler and the traveler counter act the power to defend itself. So that's my take on it if you would like to discuss or call me a moron fell free to do so kinda fits the picture to me.