More or less, yes: I played in a campaign where, due to our in-character failures to save the world, the world (and campaign) ended.I am curious to know how many people have played in a campaign (not a one-shot) that ended - or at least changed dramatically - because the PCs didn't act to stop Nyarlathotep when they needed to. Not that they tried and died, but they essentially ignored the timetable.
I DMed this one - they failed to stop the king's assassination and the overthrow of the throne (I'd planned for either outcome), but then some years later both in real time and game time they came across a device of time travel and - somewhat to my surprise - proactively decided to use it to go back in time and rearrange things such that the king survived and retained the throne (including now and then watching themselves from hiding much like the kids do at the end of Prisoner of Azkaban).Or to use another idea upthread, the duke has been assassinated and they didn't care to try and stop it. Do you plan for both outcomes? Is one as fun as the other, for you and for the players?
Depends on the scenario. If it's waiting in ambush they'll have to proactively scout ahead to notice it before they get to it; if it's wandering and the party see it then maybe they can ambush it, and so forth.One other issue: regardless of the ogre's presence on a particular path, there should still be a myriad number of ways the players can choose to encounter it, right?