After reading a lot about the campaign world and style of the Great Greyhawk and Blackmoor campaigns, I've come to realize that
persistence was one of the major implicit ideas that made the game world real: the idea that what happened in play with any group,
changed the world for all groups.
The castle, with several groups playing in it [7] was a living thing. If one group slew monsters, plundered treasure or destroyed a wall, the monsters would be dead, the treasure gone, the wall demolished for the others. If you wasted time, some other party might take advantage of you and get to the treasure first. This experience must have made it feel much more a real place to the players, than a typical "adventure" that just provides a story around the characters. You would run into houses or keeps other players had built, could meet them sometimes even as NPCs.
Hundreds of different players with yet more PCs adventured in city and castle, blasted buildings, created constructions, wiped out walls, closed passages, created new ones, trashed monsters, brought in others, and who can say what else! [15]
James Ward: I didn't find out until years later that Terry Kuntz set up a flunky hiring building in Greyhawk. Characters were constantly looking for flunkies to help in the battles. I hired one of those myself in a dwarf and raised him up to sixth level. Later I found out Terry's characters were hired by others and went back and told Terry about places in the dungeon that were worth raiding. [30.3]
The dungeon, city and rules were constantly changing and expanding. The OD&D rules are chock full of advise how to modify the dungeon [1] to keep things interesting. Gary (and later Rob) generally did not "reset" the dungeon by restocking the monsters and treasures for the next group -- what was gone was gone, but they modified the dungeon constantly by adding new levels, rooms, or changing existing ones or bringing in new monsters in longer-deserted regions.
When the setting was in constant use, we never restocked, just drafted new side and deeper levels, as it was assumed that the depredations of the cruel PC parties kept the monsters away in fear and loathing [6 #3827]
When the encounter was eliminated I simply drew a line through it, and the place was empty for the foreseeable future. [2]
In later days, Gary ran his first level of the original dungeon at conventions, and his kobolds caused numerous total party kills against players only used to balanced encounters. The kobolds, in a self-reinforcing loop, got stronger from this each time, and even deadlier for the next group. Here is a detail evolution in a post from Gary [17]:
I have run OD&D games every year at several cons for the last five or so years. I start them at 2nd level and use the old dungeon levels. So far about eight parties have been taken out by some kobolds on the 1st level. New RPGers seem to have not learned to run away when in doubt.
The first to fall used a sleep spell to get eight of the kobolds, but the six remaining ones used javelins to kill two PCs, then closed and in hand-to-hand killed all but two or the remainder of the party. One was about to kill another PC, while a second charged the m-u of the group, who turned to flee, finally. Too late, a javelin got him. Each group that died thus added to the kobolds:
1st TPK brought 12 more kobolds
2nd TPK gave them armor class of 6
3rd (near) TPK gave them all +1 HP
4th TPK added +1 damage
5th TPK added 4 2nd level and 2 3rd level kobolds
6th TPK gave them tactical manouvering and a 4th level leader
7th TPK upped AC to 5
8th TPK gave them unshakable morale
At JanCon this year the Old Guard Kobolds joined battle with a group of 8 PCs and wiped them out. I haven't decided how that will add to their combat ability, but I am considering a kobold shaman with at least two 1st level spells.
Even though in his home campaign, his group of 5th level characters then finally killed the buggers, he argued that this had been an alternate version of the castle, and bringing in the best from history, the Old Guard Kobolds with all the above advantages and with the shaman added show up in the first level of the published Castle Zagyg [7]. Essentially the idea here is the same -- even over years of play: what happened happened, and will be part of the world.
Another example is that the home game group, real-world decades later, found the hidden level where Erac had perished, and revived him.
In the words of the author of blog of holding: I’m still not sure what player skill is in OD&D, and I still think it has something to do with battle tactics, trapfinding procedures, and gaming the DM. But I’m also starting to think it has something to do with respecting the gameworld as a world.