Would be nice if randomly during the day there's a random event which can occur at any camp or village where mobs are raiding it and attacking the npc's.
If you kill one mob during these random events then you'll automatically partake in the event and if you're successful in defending the location then you get a small reward.
Any number of players can join if they're in the area, the more players join then a few more mobs will spawn.
Players would be notified in area chat like: "There is a random event occurring at location [x]" If players look at the world map and there's a random event happening then they will see a star or a symbol at the location.
Rewards could be a few potions, gold or a minion.
Just a suggestion,