Year 1 theory The inside of the traveler was first used as the black garden. In the story that was scrapped and thrown away when the alpha/pre alpha fell apart it centered around the traveler being secretly evil. Sentient technology that created the vex, tried to turn races of sapient beings and control them, got attacked, fled to our solar system, eventually made it to earth where rasputin detected an imminent catastrophic event and attacked the traveler. Traveler was dying, sent out ghosts to revive dead people who had no knowledge of its evil, calling them evil names (warlocks are evil wizards, hunters are evil predators, titans are evil mythological beings) and used then to try to revive itself. Turns out rasputin was onto it, sent in the exo stranger to tell the Guardian the truth, Guardian ends up teaming up with the awoken and getting into the black garden (inside the traveler). The garden was originally a sphere, rounded wall/floors going up into the sky. You get to the heart, kill it, stop the traveler, save the world.