Collapse

The Collapse is the period of time after the Golden Age when The Darkness destroyed most of Humanity's civilization.

History
A few centuries after the beginning of the Golden Age, an ancient enemy of The Traveler known as The Darkness suddenly struck, destroying most of humanity's interplanetary empire. Few managed to survive the devastation. Forced to withdraw to Earth, mankind's homeworld, the embattled Traveler made its final stand, where it sacrificed itself to save the remnants of humanity. The sphere now hovers over Earth, silent, dormant, and crippled, while those who survived united to build The City beneath it, establishing the last bastion of human civilization in the solar system. A powerful defensive aura remains projected over The City by The Traveler.

Aftermath
The City has come under attack throughout the years. Mysterious alien species probe its defenses for weaknesses. Guardians have harnessed The Traveler's energy to create powerful abilities, seeking to uncover the mysteries of humanity's downfall and reclaim what has been taken from them. The Guardians are all that stand between the dark forces that seek to destroy civilization and those who take refuge within The City. These exploits lead them to rediscover and reclaim old worlds that were once part of mankind's civilization, but are now occupied by deadly extraterrestrial species and threatened by the return of The Darkness. Their failure would mean the destruction of the human race.

By the time of the events of Destiny, approximately seven hundred years from the present day,  the Golden Age and the events that led to its end have largely been forgotten or passed into legend. What the Darkness is, how it attacked humanity, and how the Traveler saved humanity are unknown.