Here’s an adventure I see from time to time: The PCs are in a city or a space station or the Keep on the Borderlands and Something Weird™ is happening.
- Random people are turning purple.
- Invisible goblins are causing chaos.
- A false hydra is eating people.
- A new bratva is shaking down local business owners, triggering a gang war.
- A druid’s curse or escaped nanotech is causing the local plant life to become mobile.
The idea is that the PCs, while doing their own stuff around the village or space station or keep, will see this background stuff happening and get sucked in.
Here’s the tip: These background adventures are MUCH easier to run if the PCs do, in fact, have their own stuff to do.
This might be as simple as a standard post-adventure shopping trip: You’ve got weird stuff keyed to the general store, the magic item shop, the fletcher’s, the town square (as they pass through it), the inn where they’re staying, etc. and you’re good to go.
But I really recommend running this type of adventure in parallel with a completely unrelated adventure: So while the PCs are investigating the Neverland Murders, they keep encountering random people who have turned purple as a background detail. This lets you pace the purple people in a subtler and, often, more effective way.
(This is why I refer to these as background adventures: They play out – or, at least, start out – in the background of whatever adventure has the group’s primary focus.)
Without that parallel adventure, a background adventure tends to fail in one of two ways.
First, if there are leads the PCs can follow, the adventure will resolve too quickly. With nothing else to do, the players will immediately focus all of their attention on the not-so-background adventure, speed run the path back to whatever’s causing it, and cut short the full timeline of weirdness you had prepped. There’s nothing wrong with that, per se, but if you want the background adventure to feel like a long-term development (as opposed to a flash-in-the-pan), then you need the players’ focus to be somewhere else.
Second, if there’s nothing else going on AND there are no leads for the PCs to follow (e.g., Annie the Flower Girl turned purple, but there’s no way to figure why that happened from either Annie or her flowers), then the PCs will be left adrift — just kind of awkwardly waiting until the GM arbitrarily triggers the next background event. (And then doing so again until they finally get to an encounter with leads they can pursue.)
As long as the players have something else to actively pursue, though, you can now deliberately eschew keying access leads to the first several events in your background adventure, thereby assuring that the events have a chance to build before the PCs meaningfully engage with them. (Probably. Players can be devilishly clever at finding ways to conjure forth leads from thin air that you never suspected were there. And good on them for doing it!)
My fear in this case is that the players would forget the subtle clues over time. I guess it depends on the group and the scheduling. A group meeting every other week might run into problems. Having a player who keeps a journal is a godsend.
Session recaps and having the subtle clues be at least alluded to in various rumors the group hears might help it not fall completely off-screen for groups that are meeting less frequently. There is likely a trick in how you do that so that it doesn’t immediately become “oh that’s something we need to deal with now…” but still just be a backburner thing going on in the world.
Get the party to interact with the subtle clues. For example, if a contact that they spent time pursuing (for the unrelated adventure) refuses to keep their word and help them in a certain way lest they turn purple, they will remember that.
(The clue in this example is that action X will lead to turning purple.)
I generalize this concept as “a Living World”. Things are happening around and away from the PCs, just as much as whatever the PCs are actively “working on”. Last example from my campaign was the impending (2 months away) Lunar Eclipse. Natural magic was growing in strength while Arcane magic waned… up to the night of the eclipse when the states would flip, then just-as-slowly revert to normal. So as the party was handling a continent-jumping main quest, they saw signs of druids taking advantage of stronger magic, and wizards planning for the night of the eclipse. Nothing they had to ACT upon, but gave value to Time Passing; the PCs could harness this phenomenon (or avoid it) for themselves, or ignore it.
But, as the eclipse approached, the effects seemed to be more significant than those of historical eclipses (lunar eclipses are about every 2 years on Earth, which I used as a baseline). Again, harness or ignore? Or maybe… investigate? Investigating revealed an old adversary that had escaped them had *completed* a powerful ritual leading to Impending Doom!… and their own recent teleportation adventure had given them a possible way to get to his lair with a couple days to Do Something before the eclipse. Or… none of them used Arcane magic anyway (weird party)… maybe just let it run its course?