Status: This is something I randomly came up with, while I played Destiny. A few gamers I played with thought the idea of the Traveler being evil was awesome. So here I am, hoping to make something out of this idea

Destiny: Awakening

The Traveler, a source that was found by humans on the Moon. A miniature planet in shape that created Ghosts in it's last strength, to guide the Guardians as they fought to protect Earth. It's Light guided the Guardians and their Speaker to a utopia that never existed. Guardians fought through the Fallen, the Hive, Vex and Cabal forces to protect their world from devastation.
What if the Traveler wasn't good? Perhaps it wasn't a source of Light but eternal Darkness?
It had fooled the Guardians and other humans into thinking it was pure.. that it was protection.
It's real intentions were to use Earth as a cover, a cover for it's own evil that it would bring upon Earth when it's enemies were destroyed. Earth will lose it's Light and be lost in the Darkness.

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This is set after the Dark Below of the video game Destiny.
The Traveler used the humans as a cover, using them to destroy it's enemies.
The Fallen, Hive, Vex and Cabal weren't enemies of Earth, they were allies who were trying to help.
The Ghost knew nothing of what had happened, believing the same lies that all the humans believed.
Now with the Traveler gone and new Dark enemies pulling from Hell, the Guardians must join with the last few species they once thought to destroy.

With the Queen and the Fallen together, the Hive and Cabal have joined to help the humans regain their home and to destroy the Traveler once and for all. Maybe then, the universe may once again have it's Light.