I came up with a simple mechanic for handling events that I thought might be useful to others.
There is a deck of 12 event cards, numbered 1-12. These are shuffled together, and 3 are revealed and resolved each turn, and then the lowest number card is discarded, and a new card is drawn from the pile to replace it the following turn.
That's it -- pretty simple. What is neat about the system is that you can structure the deck so that different events are more likely to "hang around" (by giving them higher numbers) while others will almost certainly occur only once and then disappear (the ones with the lower numbers). You can do other tweaks such as shuffling other cards back into the deck, occasionally discarding the highest number card to prevent truly long term stagnation, etc.
I'm trying to implement the mechanic for my game "Sands of Time" and the events system has been a struggle throughout the game's development; I need something impactful enough that people will have to struggle against it, but not so devastating that it unduly influences the course of the game. Additionally, the system needs to be pretty quick to resolve and shouldn't involve very many player decisions. This system seems to provide a useful solution; each event is fairly minor in its effect but you face up to 3 each turn, and some of these, if they hit you turn after turn after turn, will build up in impact over time.
The system is still in pretty early testing but so far it seems interesting; the fact that you know what 2 of the 3 events are going to be gives you some ability to plan ahead. I don't actually know if having the events occur continuously until discarded is important or not; if not, it's easy enough to switch to "discard the lowest card and then shuffle all the others back into the deck".
Absolutely. In "Sands", there are 3 events because it's symmetric with the three "achievement" categories, political, cultural and civil. (Going into "too much information" mode here for a second...) The latest version has the 8 available actions in a 4x2 array and above each column is one of these three symbols, or the "unrest" symbol, and if you use one of the actions in a given column, you get a token in that achievement category (or unrest). So the three events cards go in bins that correspond to the three achievement categories, and if you used an action in the corresponding category, you incur the event in that bin.
But sure, you could go with 2, or 4 events, if that was a better fit for a given game.
I think that's the real strength of the system, it allows events that are very different in scope to be included in a game's event system. You could even (perhaps) trigger scoring rounds in this way.
In Sands, I added a rule whereby after a scoring round, you remove the [i]highest[/i] number rather than the lowest. Presumably any implementation of the mechanic would need something like this to prevent stagnation.
A similar thought is to number each event some number between 1 and 6, and then roll a d6 to see if the events stay or go (if the number rolled is = or greater than the event goes away)... so each event could be given a greater or lesser chance of ending. Similarly, instead of a die roll, the number could be attached to another part of the game. If there's X or more unrest (for example), then the event ends. Each event could be tied to a specific thing that makes sense for the event perhaps, and should count total contribution of all players.
I think those are good ideas for ways to flesh out the mechanic. I particularly like the idea that players can collectively deal with an event and remove it from the deck. I had a thought that you could give each player an individual event deck and taking certain actions lets you remove actions from the deck, but the common deck is a bit easier to implement.
-Jeff