There is the way of shaking things up with a natural disaster that wreaks havoc. But the problem here, as I believe has been mentioned many times before, is that such disasters tend to cause PvP conflicts to grind to halt. Starvation makes everything to be about food and cease fighting. Huge monster spawn make everything to be about monsters and cause fighting to cease. Disease would do something similar.
Now instead of a random punishment, you could throw in a random handout. There are many ways to do this and this is just one idea to underline the concept:
- Make one random region special in some spectacular way.
- This blessing is announced continent wide as it happens.
- The blessing stays in its place for quite some time, making it a semi-permanent feature on the map, until one day it simply vanishes
The boost, whatever it would be, should be such as to tip whatever scales there are. You would absolutely want to have it, and you would envy and fear your neighbor for having it. Players would generally react better to unearned bonus than to undeserved limitation, especially if the bonus would be something that you could conquer for yourself.
You could even have several of these regions active at the same time. The more you had them, the more effective holding on to them would be. So a giant empire would naturally want to grab as many of them as it could, while the small realms around would do whatever it takes to prevent that.
It could take many forms, but it could be something as simple as bonus in regional production (say multiplied by five or ten or something silly like that). Or it could be special rare treasures that are consumed in your region that in turn boost production (and are traded by the traders). The more of the different kind you had the more the effect would be amplified. Or whatever. I think a war over rare resources could spice things up quite a bit.
