One of the things I most like about the minimalist approach to world design I've adopted for the Dwimmermount campaign is the way it allows the players to join me in adding details to the world through play. And before anyone jumps up and notes that there's nothing new or original about this and that they've been doing that since 1978 or whenever, yes, I realize that. I'm not claiming to be innovative here. All I'm saying is that, by not having exhaustively worked out lots of world details beforehand, I gave both myself and my players the space to be creative on the fly.
Take two related cases in point, both pertaining to demihumans. Being a good pulp fantasist, I initially didn't give much thought to races like dwarves and elves, because I simply assumed they'd play a minor role in Dwimmermount, if any at all. Sure, there are the Eld, but I intended them as villains and, at any rate, I hadn't thought much about them either, since they likely wouldn't appear in the campaign until much later. But then not one but two of the players wanted to play demihumans. Since I hadn't disallowed these races as playable, I let them generate characters, though I'll admit I gritted my teeth a little, since their presence might "wreck" the humanocentric vision I had in mind for the campaign setting.
Thus were born Dordagdonar and Vladimir. In each instance, the player's portrayal eventually won me over and helped more firmly establish in my mind what other members of his character's race are like. Moreover, they've actually made me think about including other members of their races in the campaign, whereas I'd originally decided that, sure, they could play demihumans if they really, foolishly wanted to do so, but they'd be singular examples of their kind and I'd do my best not to bring up elves or dwarves in the campaign in any other context.
That's not what happened. No other elves have yet appeared in the game -- Dordagdonar's portrayal makes it clear he's unusual for his kind, who generally want nothing to do with ephemerals -- but elves now have a role in the setting at all because of the little details and ideas Dordagdonar's player has added to the game. A pogrom against elves by the Termaxians is now established history, for example, something that I'd never contemplated including, let alone turning into a possible hook for adventures, when I began the campaign. Likewise, Vladimir's player added that the dwarf became an adventurer both to acquire the funds necessary to create a son and to pay off the debt he owed to his father for having created him. Suddenly, the notion of dwarven adventurers, seeking out gold and precious gems made sense. The race was more than the butt of jokes and I decided that, while not numerous compared to humans, dwarves are probably not uncommon, with many pursuing the same avocation as Vladimir. And it was all because of things his player added over the course of the game.
I've said before that, as referee, I like to be surprised. I consider myself as much a player in the Dwimmermount campaign as those who sit around my table with character sheets in front of them. That's why I like randomness and that's why I don't detail my setting much in advance: I want to be surprised. For me -- and let me be clear: I speak only for myself -- it's hard to be surprised when I create too many details in advance. If I know who and what, say, elves are before the campaign begins, the possibility of my being surprised is lessened. It's not eliminated entirely, of course, but it's definitely lessened.
But if I have only a vague idea at the start and allow the players many opportunities to add to that vague idea, odds are much better that I will wind up with a conception of elves that's one I didn't expect. And I like that. This has happened many times in the Dwimmermount campaign: elves, dwarves, Turms Termax, Typhon, Tyche, the Thulians -- the list could go on. In each case, my original, vague notions have warped and changed, sometimes subtly, sometimes radically, over the course of a year of play. I certainly hadn't intended to portray the Termaxians as villainous at the start, for example; that portrayal simply happened in response to dice rolls, player reactions, and who knows what else.
That's the appeal of roleplaying games for me: the "spontaneous" generation of ideas I didn't plan. The Dwimmermount campaign, a year on, is much different than I expected it to be when I started planning, however minimally, for it. I think, had I prepared it in a more detailed fashion to start, it would be very different today -- perhaps just as fun but certainly not as surprising. I can't predict where the campaign will go next and I'm glad of that. Every time I think I know where the PCs will go or how they'll react, I'm delighted to be proven wrong. I want that to continue.