this is kind of vague, but do you have any ideas about a dersite breath player? breath feels like a pretty prospitian aspect, at least to me, (and only prospit dreamers have been breath players in canon which doesn't help) so i'm having trouble thinking of ways their traits could intersect. the only idea i have is that doing what you want (breath) is sometimes not doing what authority wants you to do (derse) but that's such a shallow interpretation
A way I like to interpret lunar sway is that a player's dreaming moon affects which traits of their aspect they think are "good" and which they think are "bad."
Accordingly, the player's personality and actions will tend to lean in a way that emphasizes the "good" traits and minimizes the "bad" ones, unless they are intentionally playing a villainous role.
Prospitians, in general, favor traits that have immediate benefits, especially when those traits benefit them personally, and those which encourage action and creativity.
Dersites prefer to "play the long game," favoring traits that play defensively, pay out benefits over time, and focus on introspection and self-awareness.
For example, consider Vriska and Rose: both Light players but with opposite sways. The Light aspect is about knowledge, luck, and notoriety. Vriska, a Prospit dreamer, favors the elements of luck and notoriety, but finds academia boring. She cares a lot more about a story being entertaining, and about making her seem important, than about it being accurate.
Rose, conversely, hates relying on luck and puts a lot of emphasis on acquiring knowledge, even at personal cost to herself.
Breath is about freedom, change, and detachment. It's true that Breath and Prospit sway mesh together especially well, but Derse sway brings out some really interesting things about this aspect. A Dersite hero of Breath can be frighteningly self-focused; they are an unstoppable force who will take advantage of every opportunity to get what they want.
Nothing deters them from their own whims; criticisms from their friends, society, laws, or perhaps even the physical rules of the universe -- they float above all of these, untouched. They believe in the adage of Murphy's law, "whatever can happen will happen," and seek to make sure that the things they want to happen are the *only* things that *can* happen.
If they spot a weak point where something could go off course, they will close it off. In this vein, when their plans do come to fruition, it will seem like they were really the only possible course of action all along.
They are not as fickle as their Prospitian counterparts, nor do they find randomness and unpredictability fun or comforting, but they fully embrace the inevitability of change and are quick on the draw to make sure things change in a way they find favorable.
At extremes they might act drastically under the assumption that the ends will justify the means -- even if they aren't entirely sure what exactly the ends will be. For all their plotting and scheming, the Dersite Breath player doesn't actually have a final destination in mind; their goals tend to escalate exponentially and there is always a "next step" waiting for them.
In their personal relationships, a Dersite Breath player is the kind of person that everybody *thinks* they know a lot about, but in actuality this person is very careful about what information they give out. No one would suspect them of keeping secrets because they seem very open and talkative, but this is a precisely crafted facade.
The Dersite Breath player is very savvy and pays attention to who they're talking to, and will create a new version of themselves for every situation. Everything you know about this person, you know because they *want* you to know.
This makes them an impenetrable fortress to their enemies, but sort of difficult to be friends with. They struggle to trust others, and make themselves deal with all their heavy emotions alone out of fear of vulnerability. If they decide a relationship isn't working out, they will cut it off instead of trying to fix it.
Their social circle is a mile wide but an inch deep -- they prefer to have lots of casual friends and contacts, but shy away from forming strong attachments to any of them. They don't like other people trying to take care of them and prefer to do everything themselves in order to minimize uncontrolled variables.
At points they might seem cold and uncaring, tending to view people materialistically in terms of what purpose they can serve or what they are "worth" in a given situation. Of course, the player's class will influence a lot of this information; which parts they act on and which parts they suppress or hide, the particular decisions they make, all of these depend on class and their unique personality.
I think this is a pretty good foundation on which to build a character, though.