Tbh if there's one thing that's really cool about the Destiny universe it's how they mess with the usual dichotomies. Like most settings go for light = goodness and order, darkness = evil and chaos, with no real justification other than those things traditionally being seen as good and evil. And then sometimes they try to flip it which is whatever. Saying the same thing in reverse doesn't count as new or different to me. But in Destiny they do something that's different and way more interesting imo.
Light vs Darkness is slowly revealed to be more like potential vs anti-potential. Light is about hope, possibility, and complexity, which means it sometimes risks fucking up and making things worse because a chance to do the right thing is also a chance to do the wrong thing. Like handing out power completely at random via the Ghosts leads to a lot of people abusing that power, but it's all in the hopes that enough of them will choose good to make a difference. Light is good and evil and order and chaos and everything everywhere all at once.
Meanwhile Darkness is all about simplification. It cuts off choices, resolves itself to an inevitable conclusion. It rejects dichotomies like good and evil or order and chaos as just confusing and complicated distractions that get in the way of reaching an end result that can't be averted anyway. When Oryx and his sisters make their deal with the darkness, the worms' price is that they must always obey their nature; Oryx must always explore, Xivu Arath must always fight, Savathun must always scheme. Even at the height of their power and cruelty, the one thing that most unsettled Oryx and Savathun was the possibility that they might have been able to choose differently, because that means they could have chosen wrong.
And there's so many little moments that reinforce the importance of this:
Elsie saying "A side should always be taken, even if it's the wrong one" because it's the choice itself that matters. Light is making a choice, Darkness is resigning yourself to it.
Shin asking "Are you a hero or are you a conqueror? One can harness the other, but the opposite is not true" because Darkness is all about denying possibility, it has to eliminate the Light and achieve dominance, whereas Light has the option of coexisting.
Mara's name and Sjur acknowledging that her actions "allowed the possibility of evil" and "might be responsible for more preventable suffering than anything that has ever existed" and then immediately noting all the good it did and that she cared.
It's like the more the characters question the Light, the more that they allow for shades of grey and enemies to become friends, and the more they prove that goodness comes from themselves and the choices they make rather than an external power - instead of that moving them away from the Light, it draws them closer to the philosophy it represents.
Instead of trying to flip right and wrong and ending up with the same thing but the colors are switched, Destiny does the hard work of actually answering why something is right or wrong and why it actually matters. They take this abstract conflict and connect it to feelings and questions that people have all the time, like "Does it matter if I do the right thing, even when it doesn't change anything?" and "Am I responsible for consequences outside of my control?"
My biggest hope for the story is that they take these themes and reaffirm them by having people restore the Traveler's faith again, rather than the other way around - bringing the story started in Dreams of Alpha Lupi full circle.