I don't really get how one would wake up from unconsciousness in such a place and not have it explicitly mean "this person has been up to no good." Like...sure, maybe they aren't guilty of one particular thing you thought they were, but especially as the result of a failed roll, this screams "suspicious manor-owner IS guilty!" to me. And that looks exactly like a blatant use of force: "I'm making the guilty person be this one and no other."
This puzzles me in two ways.
(1) Maybe they rescued me but thought I was dangerous? Maybe they're on holiday and their groundskeeper kidnapped me? Etc etc? I think there are multiple possibilities here - just as, when the PC in my BW game found the black arrows in the ruins of his brother's former workroom, his first instinct was to try and determine who had made them, his hope being that it would be
someone other than his brother. His hope was dashed. (I can't recall with certainty, but I'm guessing he failed an Aura-Reading check.)
(2) How is this Force? It's not any sort of manipulation of backstory to predetermine a result. There's no fudging of dice. There's no formal or informal pressure placed on permissible action declarations. Isn't this exactly how reveals unfold in DW/AW play - ie hard moves reveal unwelcome truths, including about the identities of villains.
No one is supplying them; they've been stealing them. That's why the PCs were there in the first place--a player decided he needed a magic shield, so they went looking for one, but a 6- on Supply revealed that raiding on weapon caravans had heavily affected all weapons trade (but especially magic ones). They sought out a prominent weapons-merchant (via prior contacts), who offered money and a fancy magic shield as payment for solving her "my caravans are being raided" problem.
So wouldn't it be open - for instance - that the cultists have a spy/agent among the manufacturers, or in one or more of the caravans, or at the caravanserais?
In thinking about it, perhaps I've come across what the issue might be. (I want to emphasize perhaps; I still am not sure this is more than a gut feeling that has no rational explanation.) They feel like different types of ignorance. There is "ignorance-what/who" and "ignorance-why." "Ignorance-what/who" reflects a lack of understanding about the chain of events that produced a certain result and/or the persons responsible for those events. But the chain of events had to be whatever it always was, and the persons had to be whoever they were. It feels wrong, to me, to say explicitly that it is not only unknown but unknowable what the chain of events was and who conducted them up until the point that it is declared, and then forever after that is exactly what it always was and never anything else. "Ignorance-why" reflects a lack of understanding of the motive or purpose behind some event or behavior; in principle, you already know what the event was (e.g. in your example, someone getting possessed) but are trying to figure out the motive behind it. It feels perfectly natural, to me, that you not only don't know but couldn't know what a person's true motive was until the moment of a shocking reveal, and I have no problem with it being a declaration.
This goes right back to
@Ovinomancer's post upthread - it's all just fiction being authored, and so doesn't matter.
Authoring a flower pot that was lovingly crafted by hand and has been sitting on the same sill for decades before a PC picks it up to use as an improvised weapon in a fight is no easier (nor much harder) than authoring a flower spot that spontaneously comes into being as the result of the workings of an Improbability Drive.
In all RPGing, participants all the time make up things that tend to
imply causal histories - someone must have grown the grain that was milled into the flour that the baker used to make the bread that is served to the PCs in the tavern - without those causal histories ever being spelled out. Most "story now" resolution relies on deliberately leaving much of this fiction "loose" (DW even gives it a slogan -
draw maps, leave blanks) so that it can be filled in later as is appropriate to establish further framing, or is determined by successful checks, or is helpful in narrating consequences of failure.
Locking in the "who" of causation in advance then feeds into action resolution - because now there are constraints on what further fiction can result, based on that established-but-unrevealed backstory. This is the whole premise of sandbox RPGing; but it sits in a more delicate relationship, I think, with an approach that encourages players to exercise substantial authority or at least influence over backstory (eg via asking questions of them and building on their answers), and that encourages outcomes of actions to have high salience to player-established goals/aspirations for their PCs. To spell these out: too much that is locked in, but unrevealed, can clash with the answers the players give to questions; and stuff that is locked in might turn out to provide the answer/outcome to some declared action, but at that moment of play may be of low salience to the player's established goal/aspiration for their PC.
There is a good discussion of how to handle this in the Burning Wheel Adventure Burner. And AW deals with this sort of thing, or at least closely related stuff, in its discussion of how to use fronts and their clocks.
From your posts I can't see how you reconcile your different, backstory-first approach with the standard (as in, book-prescribed) way of adjudicating and framing in DW. That's not a criticism. It's an observation.
I would argue that we can see some examples of this discontinuity playing out in ordinary fiction. Leia was established as Luke's twin sister in Return of the Jedi. But as early as the previous film, the writing includes stuff like her kissing him, which becomes deeply awkward if they were always intended to be related. It's pretty clear that they were inventing the story as they went along, retconning what they needed to (e.g. consider Luke's deep frustration at Obi-Wan's "from a certain point of view" line) in order to keep things going. That is the kind of problem I have with declaring the real killer or the like.
That just shows it can be done better or worse. All serial fiction depends on this sort of retconning. Frankly if my RPG campaigns could be half as compelling as the Star Wars trilogy I'd be pretty happy!
So while, yes, your "we found black arrows" is theoretically an alteration of the facts of the matter, in practice the only thing it actually changes about those past events is what the players know about the context of those events. The brother wasn't pure as the driven snow (unless "driven" means "driven-upon"!), he was already morally dubious. That doesn't make any part of those events play out any differently than they did before.
I personally find this a very significant misdescription.
What matters is not that black arrows were made <by someone or other>. It's that they were made <by the brother>. Hence, the possession is not <an innocent person is a victim of failed magic or Orcish magic> but rather <a sinister person finally came to their end, of being possessed by a Balrog>. That was a fundamental moment and revelation in play - unfolding over a failed Scavenging check (to use AW language, a soft move announcing the badness of the black arrows being there and hinting at worse> and then (I think) a failed Aura-Reading check (a hard move, driving home the irrevocable fact of who made the black arrows).
This was an epic moment of play, for me at least. And a regretful one, for the player who found his (as his PC's) conception of his brother dashed, all because he was greedily trying to find a different artefact in the ruined tower that he had written into his backstory. It couldn't have worked as it did if I adhered to your backstory-first norms of content-introduction. That's not a reason for you to change your practices, obviously; but is intended to illustrate why I think the situation-first/backstory-first contrast is of more than abstract theoretical interest.
