Three Things that Don't Exist in This Setting

1. Writing: The stories are, as my framing device hopefully communicates, meant to have been passed down orally for a long time, until with the (re)introduction of writing to Mars, literary versions of these tales of now-distant ancestors were set down. How much was changed in the transition is, of course, a perpetual question for our translator and their colleagues.

This is the one I think I'm most likely to have slipped up on. The idea that basically any amount of complex information can be encoded into a relatively small physical object, that someone else can then pick up in a different time and place and retrieve all that information without effort, is so baked into our understanding of the world I wouldn't be surprised if there were some places I implied transmission of information that don't really make sense for an oral culture. I first really started thinking about this when playing Final Fantasy XIV, which ostensibly takes place in a Renaissance-ish society in which officially about 50% of the population is literate. But there's basically no point in the story where anyone even questions the idea that written information won't be easily understood by those around them, and a lot of gameplay relies on this assumption too. This isn't a problem with the game per se--it just opened my eyes to how fundamental this way of interacting with the world is to us.

If I have succeeded, though, I aim to portray a society in which the spoken word is incredibly important, because it's all you have. Great deeds must be witnessed for there to be any evidence they happened; experts must travel great distances to learn from each other in person; and honour becomes an even more important concept, because you need to know you can trust someone's words not to change when you're not looking.

2. Ranged weapons: When I first described the Gordian army approaching Morgan in the Exile, I went back and forth over what weapons to describe them carrying. I almost included "rifles", but decided against it, and that's stuck: There are no guns, or even bows, on Mars. If you want to hurt someone far away, pick up something sharp and throw it.

Even if I had included guns, they wouldn't have been particularly effective on the Hounds and thus wouldn't have been used by them much anyway; but there were several compelling reasons against it. First, it parallels early medieval Ireland, which lacked bows until the Norse introduced them (actually reintroduced--they existed during prehistory, but were somehow un-invented during the iron age, and don't appear in the Ulster tales). And linked to that, it allows me to write the kind of action scenes I want, in which motorcycles and dune buggies are jousting with spears and smashing together for boarding actions. (Fury Road, an obvious inspiration of mine, itself features cars as chariots from which spears are thrown, but drawing on modern car culture it makes the driver the more prestigious role and the 'lancer' secondary; conversely in the Ulster and indeed Gordian cycles the charioteer is practically an accessory for the warrior being driven around)
I also did a lot of thinking about what exactly the Hounds should fight with. Primarily their bare hands, like Kamen Rider? Primarily weapons, like iron age and medieval warriors? I even considered a system where they could sort of "absorb" the "essence" of a weapon into a limb to power up its punches or kicks. That relied on the weapons, and the Hounds themselves, being a bit more mystical in nature, and when I locked in on the more physical mechanical vibe of everything I knew they needed to be straightforwardly fighting with steel and gasoline. But I'm not leaving Rider Kicks by the wayside, so we end up with a roughly three-tiered system, where you use your sword when you're too close for spears (or you've run out), and you use your fists when you're out of weapons altogether. Hardly innovative, but a lot more effective when those fists can strike like thunder.

(The one exception to all of this is of course Trackboar's gauntlets, which seem to be launching spears of their own accord somehow, but the writer is clearly a little confused in trying to describe this due to living in a society without any such things. Possibly a handful of devices were still around in the period described by the stories that did not then survive to the period that wrote down the stories. Or something.)

3. Sin: The morality of the characters in this story doesn't rely on concepts of ultimate good and evil. When they say the words "good" and "evil", there's no cosmological force to that; they just mean a more forceful version of "a thing I do or don't like".

Certainly they have the concept of a nice or mean person, but in their society one aspires not to 'virtue', but 'honour' (That is, 'virtue' in the spiritual sense; they say the word, but again, this is a more informal 'things I approve of'). The flipside of that is that failing to live up to these standards incurs not 'sin', but 'shame'. Shame, or the loss of honour, is only something you can incur if you had honour to begin with, so it's mostly the concern of elites and warriors. Morgan, in honour-limbo as previously discussed, is a bit more flexible on taking dishonourable actions.

(It should also be said that her own sense of morality, increasingly out of step with her colleagues', isn't derived from an idea of immutable cosmic goodness either; she's just come to have different things she thinks are good and bad, and unlike a lot of people who feel the same, she's too pissed off to bite her tongue about it anymore.)

Part of this is the characters' religion doesn't seem to be concerned with ideas of virtue, sin, penance, etc. in the way Christianity is. It's deliberate that we don't get much detail on it--in my mind it's a belief system that had lost appeal by the time the stories were written down, perhaps in favour of a more secular worldview, so our authors aren't interested in doing more than incidentally reporting that they sure believed in...some gods, back then.

But I think there's still an implied consistent throughline for what the gods of the Gordians and their contemporaries are concerned with. They swear by them, either to emphasise a declaration of intent or to make a formal pledge. They rely on them to violently distinguish truths from lies around the bonfire when holding their yearly festival. The gods are guarantors of your word--we return to the idea that in this non-literate society, trust becomes extremely important. So of course honour is highly prized, and of course you back up your declarations of faithfulness and truthfulness with a sacred undertone.

(The formulation "I swear by the god/s my people swear by", for the record, is directly from the medieval Irish sources. There's plenty of debate as to how much of the stories are preserved from antiquity and how much originates in the medieval Christian era, but they certainly acknowledged their ancient heroes were pagan; this phrasing is vague enough it could be a convenient way for the writer to cover for not knowing what the character's gods would be called, but it also could be a genuine memory, as it matches the likely historical situation of localised patron deities of specific peoples)

Finally, one thing that does exist in this story: gasoline, and therefore oil. Oil exists on Earth because there have been living creatures here for many millions of years. This is not the case on Mars, even a Mars terraformed by unknowable alien technology. One could theorise that the Burning of Olympus explains where the Martians are getting their oil up until then, but it also quite definitively cuts off that trade route, meaning whether for just the stories after it or for the whole cycle, the question remains: Where the hell are they getting their gas?
I assure you our translator would also love to know this.