this is a theory on what the traveler truly is. this is my theory. the traveler is a very conspicuous planet that orbits over earth and is meant to bring a source of light and power to the people who live under it. but is that its true purpose? what my theory basically is, is that the traveler is a source of darkness and that it spies for the all mighty vex or hive gods or something (remember that rune on the dreadnought that mentioned a god of unknown origin and we hadn't met him yet) well i believe its like the oversoul and it watches us with its creepy orb like appearance. I also think this is where the most ominous place in the whole game is located. the black garden. think about it its the perfect place as the black garden defies time and space and is in another universe or something its perfect, the traveler is the only place it can be housed as its not on Venus but its on a Venus based zone. As the portal to it is on mars there's no way it could lead to Venus as the vex can teleport there. (evidence dictates that the vex can teleport to mars from Venus and back, the reason we know is from the farming spot on mars when you spawn in). think about it. the black garden is a place where time and space doesn't exist and the traveler was originally found above mars. the place where the portal for the black garden was. also as quoted by variks in his grimoire card "the traveler this machine". Variks calls it a machine. which also backs this theory up as what species that we have found in our solar system are machines? that's right the vex. theory over.