From my discontinued custom OT server:
This is an ambitious project, I never had time to finish it but I had 2 events running on it.
World Conquering System:
Players gain an advantage based on which town they reside in, and how well the residence of that town performs compared to other towns.
On my project I had events where people would battle in various ways to achieve a common goal. Ideally these battles are big, and players are fighting for their town. By winning, every citizen of that town gains an advantage. Such as access to an isle where they can hunt monsters, or get access to trade to merchants other towns wouldn't be able to.
If another town later on would win the event, the new town gains these advantages and the previous winner looses them. Basically a town is not a place where a place just to reside in, the town itself has various advantages.
The events I had to conquer areas wasn't too special, but made with the intention of team battles.
Team of the hill in which a team had to be on the top floor of a mountain, the town that has most citizen on top of that hill for 10 minutes would win the event. If during those 10 minutes, another town would get more citizen on top of the hill, the counter would reset. So a town needed to have most citizen on top of that hill during whole 10 minutes before they could win.
Even as a town with less citizens, they could win by just killing off the exess population. These events was pvp-enforced, and once you died you could not enter the same event again.
And another event I had was a race to the top of a building kind of event, first one to the highest floor to click a win button of sorts. In order to get there, you had to climb 6-7 ladders. Using a ladder would cause a 1 min cooldown before you could climb up another ladder. The last ladder however would take 10 minutes before you could climb up, so other people had plenty of time to gather up and defend the event.
This was an always - active event. But once you climb the first ladder, a message would broadcast to all players who reside in the town who owns the area that it is under attack.
To make sure not everyone just stick to one town:
I had an advanced residence system built in. Where you have to pay money to become a citizen of a town. I would compare the town citizen population among each other and make the popular towns become more expensive, while towns with low population much cheaper to change to. I also had a cooldown restriction on it, so after becoming a citizen, you could not change to another town until x days has passed.
I would also make citizen of the same town unable to attack each other, so if you wanted to kill someone in your town, you had to change to another town before you could do so.