There are a number of different ways to adjudicate "succesfully navigating the sewers".If you've framed the PCs into a scene where they need to go hunt down an otyugh in the city underground, it's not "secret backstory" for the current location of the otyugh to be unknown---that's part of the framing of the challenge. Or is it? Depending on the rationale for play, I could easily see this going both ways. If part of the challenge is to successfully navigate the sewers, putting the party's resources at stake, keeping the location "hidden" might be part of the challenge frame. But if a player declares, "I talk to several city sanitation workers and town guards to discover the last known points of activity for the otyugh," as a GM, I'd be hard pressed to negate that player declaration if the fortune mechanic indicated a success.
This could mean that the GM already has a map of the sewers drawn, with the location of the otyugh marked on it, and the players' main goal is to declare moves which will give them information about the GM's map, including (ultimately) where the otyugh is located on it.
Or it could mean that the players declare (say) Dungeoneering checks (in 4e) or Catacombs-wise checks (as happened in my BW game), with difficulties set in whatever manner the game prescribes (in 4e this is the DC-by-level chart; in BW each skill has associated DCs for various tasks); resources are consumed in the course of resolving these checks (eg powers or rituals in 4e; perhaps fate and persona points in BW; and equipment might be used in either system); and the success or failure of these checks determines whether or not the PCs find their way through the sewers, or are lost in the sewers, or get ambushed by the otyugh, etc.
In Cortex+ Heroic this would most likely be a single check, made to establish a Tracked Down the Otyugh asset (or something similar, depending exactly how the player establishes his/her PC's goal). Success would mean that the next scene opens with the PCs having found the otyugh, and one would have the benefit of the asset. Failure could mean a number of different things, depending on how exactly it plays out, but one possibility would be that the PCs encounter the otyugh while subject to a complication; or perhaps the GM frames them into an encounter with something other than the otyugh, given that they failed to track it down.
So anyway, until we know how the resolution is going to be handled it's not even clear what it means to "keep the otyugh's location hidden": do you mean that there is a bit of information known to the GM that the players won't know until they declare the right moves to learn it? (This is how the first sort of approach would work.) Or do you mean that the players have to succeed at some other challenge before they earn the privilege of being framed into an encounter with the otyugh (or maybe if they fail they still get the otyugh encounter, but subject to some disadvantage)?
These different sorts of approaches involve different degrees of player agency over the content of the shared fiction.
I had some long discussions of this upthread.A scene where you've framed the PCs into a challenge where they need to convince a local magistrate to divulge the location of a prisoner being held at a secret location. Let's say as GM, you've created a backstory for the magistrate that he's actually under a lot of pressure because of some gambling debts he needs to pay off, and if the PCs could take care of the bookie that's owed money, the magistrate will be willing to help them.
Is this considered secret backstory? Even if the PCs could discover that information through any number of strongly telegraphed means (various streetwise and information gathering checks). How and when does this cross over from "scene framing" to "secret backstory"? Is it still "secret" if the GM has provided ample means for discovery?
My own view is that if "secret" framing is (i) knowable, and (ii) salient, and (iii) not devastating if undiscovered, then it's fair game. These are all obviously highly contextual - if the group has a long history together, and the players have extensive familiarity with the highways and byways of the GM's tricksy mind, then things might be salient that would not be salient among strangers.
"Ample means for discovery" seems to me to address (i) but not (ii). "Strongly telegraphed means" to me suggests a high degree of GM agency relative to player agency - if the situation is player-driven, then the GM shouldn't have to "telegraph" because the salience will already be implicit in the situation.
This seems to be completely orthogonal. CoC scenarios work almost entirely like this - that doesn't mean that CoC scenarios are bad idead, or for that matter that they're good ideas. Some people enjoy them; others don't.Is setting up a "hidden" victory condition at all like this a bad idea?
Clearly a lot of people like The Alexandrian's "node-based design" and "three clue rule", which is essentially a set of techniques for running a scenario along the lines that you describe (the "three clue rule" is a device for "telegraphing"; the "node-based design" is a device for accommodating different sequences of player-declared moves to try and learn the information that the GM has prepared in advance).
A significant issue here is, how are difficulties established?If this were the ONLY method to success for the challenge, I think that would obviously be a bad idea. There would always be other avenues for the PCs to find the location of the prisoner---capture / interrogate the magistrate, steal government dispatches that indicate the location of the prison, hunt down a former prisoner who would know where it is---but for this particular challenge frame, the PCs' probability of success would be exponentially easier if they "discover" the "backstory" and bring it to bear against the magistrate.
Or is this something that should be left totally "open"?
In 4e these default to a DC-by-level chart, and so there is no particular reason to think that interrogation is a (mechanically) harder way to get the information than blackmail or quid quo pro. Cortex+ uses opposed checks for everything, with dice pools coming either from character sheets or the Doom Pool; again, there's no reason to think that one way here would be mechanically easier than the other.
In BW, which uses "objective" (ie fiction-derived) difficulties rather than pacing-derived difficulties, it might be easier to interrogate the magistrate than go through the trouble of dealing with the bookie.
What seems to me to be at stake in the scenario you've set out isn't difficulty at all, but rather, what do the players want their PCs to do? Are they ruthless? (Capture and interrogate the magistrate.) Do they care about reputation? (In which case, be nice to the magistrate.) Do they want to make a friend? (In which case, help the magistrate deal with the bookie.)
This is one reason why player-driven games tend to use either pacing-derived difficulties, or provide the players with resources (like fate points etc) to modulate "objective" difficulties - so that the players can then make and act on the decisions that express their conceptions of what the situation demands (in moral, thematic, character, terms) of their PCs. Whereas in a GM-driven game, the players are perhaps more likely to be trying to ascertain the path of least difficulty so that they can have the best chance of success, which may tend to produces a more operational and expedience-driven play.
Well, do you want a game that emphasises learning stuff the GM has establishd but not revealed about the magistrate? Or that emphasises "I'm the sort of person who will cheerfully blackmail and quid quo pro my way to the top!" Different priorities for play suggest different ways of adjudicating the scene, with different amounts of player agency over the content of the shared fiction being appropriate to them.For example, should that backstory not exist at all until a player authors it? Something like, "I'm going to do some investigation around this magistrate, because I'm sure there's something shady about him I can use to pressure him---maybe, like, he's incurred some gambling debts." And then on a success, the player authored backstory is now true?
Besides everything I've said above, at this point I was wondering why anyone cares about the prisoner. Is the prisoner just a McGuffin? Which already suggests a somewhat GM-driven game. Or is there something at stake here in relation to this prisoner, this magistrate, etc?Or is this something that should be implicitly built into the scene frame by the GM? "Okay, so you need to find this prisoner because he has valuable information about [Goal X the Party Really Wants to Accomplish]. From your past success, you've been told that Magistrate Jones knows where the prison is, but you'll need to convince him to give that information to you. Some cursory "street investigation" into Magistrate Jones reveals that there may be a way for you to put the screws to him and get what you need."
This takes me back to the questions about resolution. Until we know how resolution works (again, contrast plotting positions on a map with adjudicating a skill challenge), ti's not even clear what "updating" or "modifyting" or "improvising" look like.even if I as GM have "pre-authored" elements of a scene frame, those shouldn't be the only possibilities embedded into the frame, and I as GM should be open to improvising/updating/modifying elements based on PC action declaration and intent.