werecorpse
Adventurer
Much of what you refer to as contrivance is just "in games" plans being put into effect. The op refers to the Rohirrim arriving on the dawn of the third day as if it's some sort of author based contrivance. In fact Gandalf leaves before the siege commences so he can locate the Rohirrim and says look for me on the dawn of the third day - so it's not some amazing conicidence that the Rohirrim turn up. It's a plan by a guy who is pretty clever. If that was a game I was running the issue would be can you survive until dawn of the third day when the cavalry are literally expected to arrive.
My "contrivance" that I use in running plots is to have it that the paths of the bad guys and the PC's keep crossing. Each time they may meet or may not. But that's because the story we are telling is about them, not some other bunch of heroes who are presumably meeting some other n'er do wells in some other plot line. If the PC's ignore or fail to stop the bad guys they just advance the evil scheme a bit.
For example here is the outline of a plot where a bad guy plans to bind a demon to himself to gain power
1. Bad guy steals magic book with ritual from players mentor
2. Bad guy obtains necessary weird ritual stuff - a manticore skin (a manticore happens to be an enemy the players meet in another adventure)
3. Bad guy captures sacrifices and holds them somewhere
4. Bad guy performs ritual in a certain spot at a certain time (by a lake on the full moon say)
At point 1, 2 or 3 the players might figure out who the bad guy is but at least will get an understanding of the plot. They might rescue the captives and foil the preparations etc. by the time 4 happens they have a pretty good idea what is going on and where it's likely to happen so the, turning up is just good sense. But if they don't, that's fine I have a bad guy who then starts another plot - to summon a death knight servant or dominate the local Duke etc.
If they never stop him he eventually succeeds in his plots and lives evilly ever after.
Let's say the players figure out where the ritual sacrifices are being kept by the bad guys hobgoblin allies. They free them and find out who the bad guy is and go kill him. That end isn't contrived except that it was contrived that they would cross paths - but that's because that bad guy needed the mentors book, and the skin of manticore they happened to kill etc etc. we are not telling the story about the Orc necromancer who finds some relics that enable him to build a bone colossus - that story is the story of that other group of NPC adventurers.
In my world amazing things are happening all over the place - but the story we are telling is just about the players bit of amazingness.
My "contrivance" that I use in running plots is to have it that the paths of the bad guys and the PC's keep crossing. Each time they may meet or may not. But that's because the story we are telling is about them, not some other bunch of heroes who are presumably meeting some other n'er do wells in some other plot line. If the PC's ignore or fail to stop the bad guys they just advance the evil scheme a bit.
For example here is the outline of a plot where a bad guy plans to bind a demon to himself to gain power
1. Bad guy steals magic book with ritual from players mentor
2. Bad guy obtains necessary weird ritual stuff - a manticore skin (a manticore happens to be an enemy the players meet in another adventure)
3. Bad guy captures sacrifices and holds them somewhere
4. Bad guy performs ritual in a certain spot at a certain time (by a lake on the full moon say)
At point 1, 2 or 3 the players might figure out who the bad guy is but at least will get an understanding of the plot. They might rescue the captives and foil the preparations etc. by the time 4 happens they have a pretty good idea what is going on and where it's likely to happen so the, turning up is just good sense. But if they don't, that's fine I have a bad guy who then starts another plot - to summon a death knight servant or dominate the local Duke etc.
If they never stop him he eventually succeeds in his plots and lives evilly ever after.
Let's say the players figure out where the ritual sacrifices are being kept by the bad guys hobgoblin allies. They free them and find out who the bad guy is and go kill him. That end isn't contrived except that it was contrived that they would cross paths - but that's because that bad guy needed the mentors book, and the skin of manticore they happened to kill etc etc. we are not telling the story about the Orc necromancer who finds some relics that enable him to build a bone colossus - that story is the story of that other group of NPC adventurers.
In my world amazing things are happening all over the place - but the story we are telling is just about the players bit of amazingness.