I could see the popularity of a Morrowind-style MMO. Here's how I'd do it:
Players start out as chumps just off a boat / waking up in bed / whatever. The local news is there's a mental plague going around where everyone thinks he's some kind of messiah ready to save the world! The authorities watch with increasing concern.
Players run around initially doing shitty errands like in any ES or MMO. Maybe trying to earn enough dungeon cred to join one of the noble houses or guilds as an Earnest Newbie.
Once you get enough of the little dungeons scattered around, which have enemies that seem to come back every once in a while. WTF is up with these respawning bandits and rats? Also sometimes you find a cave with friendly bandits who say they're with your noble house and sometimes you get a quest to support them in an assault against some other thing.
Then you get up in the ranks of a noble house enough to be allowed to enter the main fortress. Up until now it's been lame little three-room training halls and storage warehouses, but now you wander past deathtraps and statuary as you make your way into your new digs in the fort. Occasionally folks from outside will try to break in at a secret entrance or through the sewers.
Here's what's really going on:
Every noble house is trying to gather monsters, foreign bandits, etc. to make a play against other noble houses and maybe bring forth a new Emperor. But they can't just have these scrubs wandering the streets. So they house them in local caves and dungeons until the time is ripe to use them against some other noble house.
Also guilds and noble houses get to build big complexes using modular parts, including traps and locks and hired guards and merchants and stuff. But the larger the complex, the more secret entrances it has to have. Each secret entrance must be a certain distance from other entrances and it must connect with all other entrances in some way, and it must be closer to a nice room (vault, merchant, trainer, workshop, great hall) than to another entrance. This allows people to sneak in and fight you, and you can't just have all your secret entrances leading to a trapped hall of death and then a blank dead end.
It also costs a lot of resources to build, so the guild wants to get a lot of lumber, quarried stone, metal, bonemold, ebony, etc. They get that by controlling resource sites in the countryside, villages, dungeons, etc. To support the people working you need food, tools, clothes, and guards. So you need workshops to make goods or else buy them from whoever you can in town.
Lowbie players will gather resources, defend resource sites, craft goods, transport resources and goods (caravans), etc. as their skills and inclinations suggest.
Higher-ranked players in their organizations will play more of a strategic game, directing their forces and working toward some specific goal. Maybe at the bottom of one dungeon there's an imprisoned monster that you can recruit to help fight. But to get it you need to occupy the dungeon, reach its lair, and have the Seven Seals of Samanda or whatever.
There's also an external threat, which tends to attack the more powerful organizations' things more than the weak ones. This means if your org is getting really powerful your difficulty ramps up and if you lose a step you'll get busted down a few pegs. All procedurally, not much input from the admins.
Inspiration from Planetside and Natural Selection, pretty much.