This a theory I had put into words today to a friend over Xbox Live: "The Vex are.. of what we know - supremely intelligent and adaptable." "And what else do we know, may share those traits?" "..The traveler of course." "It travels from planet to planet, opening it, terraforming it, adapting planets." "For what?" "The Traveler has a secret." "The traveler visited planets in our system.. and transformed them." "Gave them practically everything to spawn life." "But it left something to tend after this garden.." "The Vex." "It buries them deep inside" "But it has to surround the planet." "Mercury was first to be impregnated with the Vex." "Mercury was engulfed by the traveler.. perhaps it began here." "The traveler peeled from mercury, closed up, and traveled to Venus" "Notice how far-long Venus is.. in the cycle." "Look at Mercury.. there's similarities." "Venus was inhabited by the traveler, and just like Mercury, the Traveler peeled from Venus and took towards Mars" "The reason it went to Mars, not Earth, is because Earth it was December, and Earth is passed Mars on this calendar date" "At Mars, the Traveler did the same thing, but did something entirely different." "It sensed the incoming darkness." "It took on the darkness at Mars.. and held it back, claimed a fragment of it and stored it beyond a gate." "Within this gate, was the dimension of the Hive" "Not knowing what the Vex had found, or able to analyze it, a protocol activated to cease collecting and begin worship" "The Traveler, retreated to Earth, not fully built by the Vex in time to be in full power of its light." "The Darkness had weakened the working force of the Vex by claiming those Vex who sought worship of the Heart of the Black Garden." "The Traveler came to earth, but not fully intact. It's only powers were to revive the dead to help fight the darkness so it can heal.. a final defense protocol" "The Humans probably never survived the collapse without the Vex, who probably dissappeared before they were aware of their existence" "The onboard Vex were probably transported back into the traveler to continue building it" "The Ghosts were built to revive fallen guardians" "The Ghosts use the species of a living world to push back the darkness and use their subjective intelligence to make conscious ideas of what the darkness is" "The Traveler then learns this info through a ghost, and uses it to further calculate the Darkness." "The Traveler, when built, never knew such a thing as the darkness." "The Vex it had created, merely existed to tend to their planets, and to exist till the end of time" "But When the Traveler met the Darkness, it activated the Vex to turn hostile, in order to protect its installations." "Vex traveling between future and past collided and began simulating the end of the universe through the darkness" "This pushed the Vex to begin understanding military operations, and to try to defeat it" "The Vex on Mars however are visited by future vex in a portal the Black Garden, a Hive realm." "These Vex worship the Darkness in their world" "They drained light from the traveler and prevented it from being built fully." "They also brought back the Hive." "The Hive wasn't looking to take Mars, rather, it wanted the Traveler's light" "The Traveler in this system is like a tiny candle lit, and the Hive are trying to extinguish it" "The Hive inhabited the Moon, setting up an offensive to take the Traveler." "The Hive lord Crota, behind the assault is spawned on the Moon." "Guardians fall to Crota and lose the Moon" "Then.. Crota slept." "The Hive practically relied on Crota to lead the attack on Earth, but they require a new champion from Oryx" "Or.. perhaps oryx himself." "The Traveler is so sought after because he had built the planets so that Hive could not inhabit them." "The Hive are after the Traveler now, and the Vex are attempting to make their way to Earth to protect the Traveler." "The Fallen were actually an old species of aliens from Venus or Mercury" "I can speculate that the Fallen and the Hive are identical, but the Fallen exist in this realm of existence, and the Hive within another realm." "This is why the Fallen fight the Hive, and the Hive fights them back" "These two enemies also want the Traveler, but the Fallen are only suddenly aware of the Vex. The Hive already understand them." "The Fallen view the Vex as enemies, and the traveler once protected them from these enemies" "The Fallen built the servitors to figure out the Vex like the traveler had already known and destroy them or keep them away" "The Fallen still want to capture the Traveler and research it further" "We're in between the Vex, Hive, Cabal and Fallen as we protect the Traveler until the Vex arrive" "(As an added thought: The Vex activated the dead organism or went into military mode and attacked the life on all the planets - attempting to gain military strength" So that's it. Hope you enjoy it. It know it's long, but sorry, no tl;dr