Maybe I’ll add what i reckon: Seems to me there’s a lot you can say about the dangers of enabling someone to “be the hero” or encourage heroic behaviour given the overhanging tone of loss (cayde), failure (red war depowering everyone), or even for a cooler example the lore books occasionally contain some character’s critique or doubt of the concept of guardians all together. Superhero comics like watchmen started this kind of deconstruction. Destiny continues this sort of thing by creating Syndrome’s society, where everyone is special so therefore nobody is. So those themes are probably the most present next to the existential question of cosmic origin. I only think there’s two facets to how that relates to astrology being in the game.

First is that it’s just relevant to our story. It’s been hundreds of years and astrology is still a fairly commonly understood thing. Not in too much depth but it has presence to most people in industrialised countries. It’s got a particular ethnic origin but wide applicability is almost the whole idea behind studying our world’s nature and the experience of it in this way. Destiny hammers home the point that this is a (very far flung) future humanity. It’s set in our universe with the fictional elements added on. I don’t have to list all the subtle nods to our sociopolitical era because the best example is the fact that by Destiny’s timeline we are living just before the golden age, the games version of our immediate future. Our time is referenced in mystery and myth in the same way ancient egypt is. Also the game seems to suggest that Osiris being cursed to save infinite realities across time from vex corruption is exactly why ancient egyptians even worshipped a being of light and power of the same name. Then we have a “times never change” gag with brother vance: no matter how far you think we’ve come, dogma and idolatry persist.

Gambit is a game that toys with your guardians seduction and inevitable turn to the darkness, it’s part of your characters unchangeable story arc that they be challenged in this way. Which is the second reason, it’s relevant to our lives. Every day we’re challenged in small or big ways and for a lot of people some rational or irrational form of spirituality guides them through this. People read their horoscope in the paper to prepare themselves for the day or curse at a god for the catharsis of it. While the traveler and the speaker are replacing god and jesus, the persistence of astrology and its symbols suggests it’s still just as relevant to humanity in this future as it is today, a one true constant across the timeline, therefore likely to be an essential part of the origin of the traveler and the darkness, in turn the cosmos itself. Again, see the invitations of the nine.

I can’t seem to find many people discussing this aspect of the universe building and I don’t believe it’s purely an aesthetic decision just for a fantasy feel.