The Light (The Gardener) is a paracausal force that is associated with gifting, life, and resurrection. It is the power that helped birth the guardians with the ghosts from the traveler. This power expands and grows the universe to become more complex and nuanced.
The Darkness (The Winnower) is a paracausal force that is associated with taking, death, and finality. It is the power that Oryx and the Hive followed from The Witness and the sword logic; the more you kill, the more powerful you become. This power shrinks the universe down to the most simple common denominator of kill or be killed, and creating The Final Shape of the Universe.
WE (the Player(s)) are a paracausal force and entity that creates choice, fate, and Destiny. We’re the force that prevents our character from turning evil or genocidal when wielding the Darkness (Stasis for example).
Our characters in particular are directly influenced by our actions like the Traveler and the Witness are by the Light and the Dark. Both are neutral forces that have agents with agendas, but we are a force with an agenda ourselves that control our relatively neutral agent, ensuring its victory.
What if everything we do is akin to a paracausal act. When our character dies in a darkness zone of a raid encounter, they die in that timeline for good. Whenever we restart, a new timeline is created where different things occur (a new raid strategy, killing a certain ad, popping a super, reviving a teammate, etc.) that result in different outcomes. Completing the raid encounter for example.
Defeating Oryx resulted in many death timelines until a timeline is created where our guardians succeed. Defeating Riven, Rhulk, overcoming Vex simulations, saving Saint, defeating Savathûn, and later defeating The Witness will all be due to OUR influence.
The Light gives, the Darkness takes, We (Symmetry) choose. We choose who wins and loses in the cosmic war of light vs darkness. WE are the only paracausal power that can GIVE the Guardians a victory and TAKE the Witness’ victory away.
We’re a Guardian ourselves, and Guardians Make Their Own Fate!
Edit: The prophecy on the wall of the pyramid will ultimately fail. The final goal of the Witness is to end the universe (“enough death, enough life”). It may be successful in everything else, but The Witness won’t be killing everybody, WE will be killing IT!
Light and Dark are just a form of power. The Gardner and Winnower made them to reflect their philosophies and goals.
Light doesn’t give. Warlords proved that.
Darkness doesn’t take. We proved that by harnessing it for good.
Symmetry isn’t about choice. Ulan-Tans idea was that Dark and Light can’t exist without one another.
Back when this was written, both powers came from the Traveler. There was no Winnower. So to truly stop the forces of the Darkness, we would have to sacrifice our Light.
Base D2 carried Symmetry over with a slight hint in the form of Ulan-Tan having a lost sector named after him and the base ending cutscene hinting both powers
The end of the Dark and Light saga will follow the original idea. Both powers are going away, likely by force.