say the rumours are both true and the PCs will meet Orcs if they go one way and spiders if they go the other; but in either case they're also going to meet a nasty Druid and his pet Displacer Beasts shortly afterward. What then? The Druid's not on the rumours list and thus the PCs don't know he's out there or where he might be - for all the players know he was rolled on a wandering encounters table.
Whether or not this is illusionism depends on details not provided in the example - eg what did the GM tell to, and/or imply to, the players about the decision-making process.
But it doesn't sound like it involves very much player agency. The GM seems to be deciding what play is going to be about (ie this druid encounter).
Maybe I intended to prep for both orcs and spiders, but my pet iguana ate the MM pages containing the rules fore spiders so now I have only the orc encounter prepped.
It seems that the GM could just tell the players
today it's going to be Orcs, because that's all we've got!
Anyway, as the characters arrive to the Gnarly Forest they come upon several slain spiders, and if they investigate they manage to find some arrows of orcish manufacture. But there are no orcs in the Gnarly Forest, and the closest orc settlement in the Grim Chasm is a significant distance away! What are the orcs doing here? This is not just some random orc raiding party, the spiders have nothing of value. Has someone send the orcs here and to what end? So now instead of just one random encounter with orcs on the orc territory, the encounter will now be tied to an emerging sublot. The actions of PCs did affect things, just not in the way they may have anticipated.
This may or may not involve illusionism, ie, a false belief engendered in the players that their choices of action declaration will affect the content of the fiction.
As to whether or not it involves player agency,
where does the mystery come from?
Why orcs-vs-spiders? If this is all being set up by the GM, there seems to be little or no player agency.
Yes, this is critical. Nearly all the examples I see, of choosing left paths or right paths, of orcs or spiders, fail to examine the real questions of agency such as:
- Who created the need for my character to travel at all?
- Who authored where my character needed to go?
- Who created the reason for my character going there?
- What is my character going to do when they get there?
Most discussions on the topic implicitly include the answers:
- The GM
- The GM
- The GM
- The thing the GM says needs doing
In other words, GM force is so heavily presupposed in nearly all the given examples that there's no point engaging them.
Player agency is a loop which has to begin from the first moment of play (or not). From that point on the creation of purpose for the character doesn't change hands - either the player gets to do it explicitly, or the GM does it implicitly.
And if it features agency then play from that point on is, as you describe, a cycle of action declaration and action resolution until the player decides their purpose is achieved or failed or that the character has changed and their purpose has shifted.
Your point about presupposition of GM decision-making is evident, I think, in the examples of the druid-with-displacer-beast, and in the example of orcs-vs-spiders.
A concomitant of that presupposition is a narrow conception of both
action declaration and
action resolution.
If action declaration is thought of simply as
we go to place X, then in a typical map-and-key approach to setting design and travel resolution there will be no player agency. The players move their tokens about the gameboard, but the GM is deciding at each moment of play what actually happens in the game.
As I posted upthread it is possible to use map-and-key techniques in a game that involves player agency, by relying on the phenomenon of
time: initial moments of play are low-agency, as the players (metaphorically, at least) turn over the board tiles and learn what is under them; but subsequent moments of play are high-agency, as the players use the information they have acquired to formulate and execute plans for extraction of assets from tiles.
Because of the role that time plays in this approach, there are essential constraints that must apply if agency is to be generated and preserved: most importantly, the GM can't change the gameboard once the players start exploring it!
Hence the fundamental conflict between the sort of play I've just described, and a "living, breathing world". Even Gygax fell foul of this contradiction in his published rulebooks for AD&D: his advice in the PHB, under the heading Successful Adventures, presupposes that the dungeon situation is largely static and hence that players can engage in meaningful exploration and planning; but in his DMG he gives advice on how to make dungeons non-static, which will have the effect of rendering the exploration and planning largely meaningless (unless the dynamics unfold in
very predictable ways such that the players can account for them in their planning).
The only way I know of to combine a "living, breathing world" with genuine player agency is to expressly or implicitly expand the scope of action declaration:
we go to place X to achieve goal Y. And if the GM doesn't just say "yes", then there needs to be a meaningful way of resolving this action declaration.
There are a lot of options here: anything from Wises-checks (as per Burning Wheel), to letting the PCs turn up but framing them into a situation where their goal Y is at stake (my Classic Traveller play often looks like this; so does my Prince Valiant play), to various forms of checks to see how the travel goes relative to the goal (I've done this in Burning Wheel - Orienteering check where the consequence of failure was that a renegade elf had interposed himself between the PCs (who included a rather self-consciously upright elf) and Y - and in Cortex+ Heroic - checks in an action scene to eliminate Scene Distinctions which, if not eliminated, posit that Y has not been attained or remains unattainable), or probably other approaches I'm not thinking of at the moment.
But what is key to all of them is that
the players are the ones who are giving content and meaning to the goal Y; and the connection of travel to X in order to achieve Y is up for grabs, in the moment of play, as an outcome of action resolution. And one upshot of all of them is that if the PCs are at X but Y has eluded them, the players know why in both fictional and real-world terms:
our negotiations with those sect members didn't work out (failed social resolution);
we took too long and lacked sufficient endurance to cross the Bright Desert in good order (failed Orienteering resolution);
I guess so-and-so wasn't the good guy I thought he was (this one is from Burning Wheel, and was actually the consequence of a failed Scavenging check in so-and-so's old headquarters);
the Nazgul didn't stop us reaching Forochel, but - almost as if there were forces in the world working against us! - the orcs had already made off with the re-discovered palantir (this one was in Cortex+ LotR, with a 2d12 doom pool expenditure to end the scene, made possible because Gandalf's flagrant displays of power to defeat the Nazgul grew the doom pool unusually rapidly); etc.
The other upshot, of course, is that if the players succeed on the relevant checks then the PCs get Y: they destroy the conspirators lab and thereby put an end to the bioweapons plot; they arrive in Cyprus and take their first castle; they catch and defeat the orcs (but don't find the palantir - more Gandalf cutting loose => another 2d12 spent to end the scene); Thurgon and Aramina find Evard's tower north of the Jewel river, where the tales and rumours said it could be found (successful Great Masters-wise check); etc.
If the players establish their PCs' goals, and can - via action resolution - attain them, then in my view the players have agency. The GM is not the sole author of the important parts of the fiction.
But if all the players can do is change some superficial set dressing -
we're in the Gnarly Forest, not the Grim Chasm - but everything that matters is decided by the GM (
you meet a druid and displacer beast;
you defeat them, but an apprentice rises up to keep their evil schemes alive;
the orcs are also opposed to the druid's spider minions, but allying with the orcs just causes grief and backstabbing no matter what you do; etc), then it's obvious that the players have no real agency.