That looks like some cool stuff there.
However, it's perhaps a tangential example to what I'm saying, for these reasons:
1. In your write-up it seems the various locations referenced are quite close together - each a staircase apart, if I read it right - and so there's very limited opportunity (or need) to introduce intersections and-or other geographical features.
2. This seems to be an example of epic-level play (one of the PCs is already a god, for Pete's sake!) near or at the end of a campaign, which implies most of the fundamental choices have already been made and any earlier distractions long since dealt with. It's a bit late to be introducing something as trivial as a slave being beaten.

Yet with that said, you were still introducing DM-driven complications...
3. Further to 2 above, we don't see here how direct or indirect the party's path has been to get to this point; how often they veered off course, or whether there was any point when they could have lost the trail of the story entirely and thus never got this far at all.
The GM introduces complications, but look at how and why that is being done:
Appropriately enough, it was the player of the ridiculously zealous paladin of the Raven Queen who first conjectured that the subject of the riddle was the Raven Queen herself . . .
The sphinx accepted it, but insisted that they also tell him whose pride will be cured. After generic answers ("everyone dies"), which did not really satisfy the sphinx, the fighter/cleric answered "Us". The sphinx replied "Well, yes, you," and this was the clue for the player of the invoker/wizard, who answered "The gods" - because the fighter/cleric is now God of Jailing, Pain and Torture (having taken up Torog's portfolio). . . .
The paladin looked in the cleansed pool to see what he could see, and saw episodes from the past depicting the Raven Queen's accretion of domains (fate from Lolth, in return for helping Corellon against her; winter from Khala, in return for sending her into death at the behest of the other gods); and then also the future, of a perfect world reborn following the destruction of the Dusk War, with her as ruler. . . .
I explained to the player of the fighter/cleric (who is now the god of imprisonment, and also has a theme that gives him a connection to primordial earth) that he could sense the Elemental Chaos surging up through the earth of the mortal world (because (i) Torog can no longer hold it back, and (ii) the Abyss, having been sealed, is no longer sucking it down the other way); and as a result, an ancient abomination sealed in the earth had been awakened from its slumber and would soon makes it way up to the surface of the world. I then filled them in on my version of the Tarrasque (the MM version with MM3 damage and a few tweaks to help it with action economy). This created suitable consternation, and was taken as another sign of the impending Dusk War. . . .
This room had a statue in each of four corners - the Raven Queen mortal, ruling death, ruling fate and ruling winter. The fifth statute faced a large altar, and showed her in her future state, as universal ruler. The murals and reliefs here showed the future (continuing the theme of the rooms: the entry room showed her mortal life; the principal room her magical life, including her passage into death; this room her future as a god). I made up some salient images, based on important events of the campaign: an image of the Wolf-Spider; an image of the a great staff or rod with six dividing lines on it (ie the completed Rod of 7 Parts, which is to be the trigger for the Dusk War); an image of an earthmote eclipsing the sun (the players don't know what this one is yet, though in principle they should, so I'll leave it unexplained for now); an image of a bridge with an armoured knight on it, or perhaps astride it - this was not clear given the "flat-ness" of the perspective, and the presence of horns on the knight was also hard to discern (the players immediately recognised this as the paladin taking charge of The Bridge That Can Be Traversed But Once); and an image of the tarrasque wreaking havoc. . . .
Closer inspection showed that where it was possible the queen's name had once been written on the walls, this had been erased. The invoker/wizard decided to test whether this could be undone, by using a Make Whole ritual: he made a DC 52 Arcana check, and was able to do so (though losing a third of his (less than max) hp in the process, from forcing through the wards of the Mausoleum). Which resulted in him learning the name of the Raven Queen. And becoming more concerned than ever that it is vulnerable to others learning it to.
All the complications, and the increasing of pressure on the players, is done by reference to PC dramatic needs. This is what player-driven RPGing looks like: the GM frames scenes, and "[e]ach scene is an interesting situation in relation to the premise of the setting or the character (or wherever the premise comes from, depends on the game). The GM describes a situation that provokes choices on the part of the character."
There is no "veering off course" or "staying on course".
There is no pre-determined course. There's just
these PCs, with
these needs, whose players make
these choices when the GM confronts them with
this situation. Of course at epic tier the in-game stakes are higher; but the methods are no different.
That sort of game really seems to assume the players will be quite goal-oriented
Yes. This is why they have mechanics like Beliefs or Milestones; or why, in my 4e game, I asked the players at the start of the game to give their PCs a loyalty, and a reason to be ready to fight goblins.
I'd rather see the DM framing scenes and introducing vignettes in passing that are intended to try and divert them from their goals or frustrate them from achieving such, rather than just relying on the luck of the dice to provide you with these opportunities.
But you don't need to try and divert. What does that add? Stories are about challenges to the satisfaction of dramatic need. So you present challenges and complications just as Eero Tuovinen describes - eg Can I save the world from the tarrasque, which will probably need the help of my Raven Queen-worshipping friends, without helping them make the Raven Queen the ruler of the cosmos? Does becoming a god help me stand against her, or make me more likely to be humbled by her? Or, for a different PC: Is the only way to keep the Raven Queen's name safe from others learning it for me to learn it?
This will make stuff happen.
pemerton said:
you are assuming (1) that there are no failed checks
Yes I am, that's what point 3 (repeat until success) covers.
I'm sure I've posted multiple times upthread that this sort of RPGing depends on finality in resolution. There are no retries.
And if a group of players aren't necessarily that goal-oriented and just want to play for gits and shiggles, how's that gonna work?
Maybe not so well. So maybe the GM starts exercising more agency. But it's hard for me to see that a non goal-oriented, "gits and shiggles" player is at the same time one who is exercising lots of agency over the content of the shared fiction.