The Traveler's origins are unknown. When it arrived, humanity first discovered it on Mars. It sparked a Golden Age of humanity that allowed humans to migrate from Earth to colonize other planets within the Solar System. Some speculate that the Traveler is a large vessel; others believe that it is a sentient being or artificial intelligence and some may even consider it a deity. As of yet its true nature is unknown.
The Traveler is credited with humanity's survival during the Collapse of the Golden Age. After the Traveler sacrificed itself to save humanity, it remained floating not far from the Earth's surface, and became silent and dormant. The City was built in its shadow and under its protection, where its inhabitants are temporarily safe from the threat of the Darkness.
The Traveler grants some of its mysterious powers to the Guardians that take the form of usable abilities in-game. Ghosts, the personal artificially intelligent companions of Guardians, were made by the Traveler itself in its dying breath. Within the Tower, The Speaker acts as the representative of the Traveler.