Brenden brought up the idea of a persistent campaign setting. He name-checked Robert Conley, who then further discussed the idea.
Basically it's the old-school idea of a persistent world that different gamers and/or gaming groups interact with. It's not reset for each group, but rather any game changes effect all groups that follow.
When I read Brenden's post, I was a bit surprised - doesn't everyone do this?
- In my very early D&D days, we'd run group after group through B2, T1, X1, or S1 and the next group would only encounter what was left after the first group made its pass.
- In my high school days, I drew up a game world and ran people through it. We had a "major" gaming group, and then, for the guys who had much more time to play, a "secondary" group of (initially) lower-level guys. These groups had some interesting overlap - at least once, a "major" group PC assigned a "secondary" group PC a quest and sent them to mop up some dungeon they didn't have time to deal with. Eventually both groups converged in a game-finale sacking of a castle (Great Stoney, from Dragon Magazine). The "secondary" group fought the flunkies and cannon fodder, and the "major" guys fought a major devil and a bunch of githyanki knights and assorted nasties.
- When we switched to Rolemaster, I initially had one group go through the Known Worlds setting, and then switched to Greyhawk for a fresh start. We'd done some Greyhawk D&D adventuring and I had NPCs from that game appear in my Rolemaster games.
- Finally we really got going with GURPS 1st edition. I had just gotten the grey box Forgotten Realms, so I set it there. I ran so many groups there from around 1985 until the early 90s that I lost track of them - there was one or two abortive starts and then a big campaign that rampaged around the Inner Sea, Thay, and eventually the Savage Frontier and down as far south as the deep jungles. Many players came and went. Then I stopped playing for a bit, but when I re-started in 1994 with new players, I set it in the Forgotten Realms. They met retired PCs and NPCs from the first group and interacted with them. They followed up on half-done adventures from the first group. And eventually, they got scattered and beaten up - and split into two groups in the process.
Amusingly, one PC - Malkav the Apocalypse, self-proclaimed son of the god Malar, solo adventured for a while. He caused much havoc down the line. He got rescued by Malar cultists, beat them up and ran off with their stuff, founded an empire (while an NPC - we did it by narrative), fathered a son (a later PC of the same player), and then sent assassins after his son to "toughen him up." That later PC joined another group of PCs, who eventually ended up hiring an NPC who worked for Malkav and who led them to their doom.
Characters wove in and out of those games - they often encountered each other, or their kids went adventuring with a new group, or fought organizations founded by previous PCs, or got handed down magic items from older PCs. So as the GM I say "That +2 axe you got from Skullcrusher Kurgan was picked up off an ogre guard in that big fight I told you about the day you generated your PCs." Or a player says "A dragon? My uncle Ayyub once slew a dragon" to his fellow players whose previous guys adventured with Ayyub and never met no dragon.
Experienced PCs from one group - in fact the two earliest PCs from the 1994 group - eventually ended up frozen in stasis and freed much later, and joined the very last group of PCs to adventure in that world.
Again, the changes were all persistent and crossed groups and lasted over time.
So it's actually my normal game mode. My previous game - set against in the D&D Known Worlds/Mystara, was deliberately designed as a one-group location. It wasn't meant to persist, merely to be a locational vehicle to tell the story of that group's adventures.
My current game is set in a very vague world, entirely set up to justify the dungeon-bashing we want to do. I've already told my players that if, say, we do another DF game but with sci-fi crossovers, I'd set it on some remote part of the same world. Far enough to explain a lack of cross-contamination but close enough to allow a crossover if we wanted to do so (and to use the same rule base).
Some of Brenden's points as worth extra discussion:
"What if multiple groups are playing at the same time and affect each other? What if one group plays in "the past" with regard to other groups? It seems like temporal paradox could potentially be a problem, though realistically I don't think it would be difficult to avoid."
Just let that happen, it'll work out. It's easier to play downstream than upstream, but if you insist on doing upstream play, set it in an area remote from the other play areas so they can affect places before the downstream groups visit them.
Paraphrasing here - can the GM become too concerned with the campaign over the players?
Hell yes, and we call that "the published Forgotten Realms stuff." Good luck trying to change that world - the GM really does need to consciously let the players trash the world. If some parts are meant to be static, so be it, you can make it so and even tell the players it's meant to be so. But you have to realize it's just a location for adventures, and let it go. You can benefit from a good bit of background, and the play will generate even more.
The players can get a bit concerned, though, so you can't willy nilly blow the whole world up as a campaign event. It'll annoy them that their retired lord spent real-world years clearing out a domain and you just nuked it to bother their new characters. If you need a clean-slate change, put the game world down and play on another one for a while.
Finally, let me end by saying this: this is a great way to play, as a GM and as a player. The players know the world because they helped shape it, even the parts their (current) characters don't. Competitive groups - thinking of Jeff's Wessex games here - are effectively cooperating in an endeavor but racing for the glory and loot. With the same players over and over, they own the world.
If you haven't tried a persistent game world, give it a go.