Have you ever played a PnP game where there was more then ONE DM dming it ? I know I haven't nor would I have ever let a second DM run my game. Because only I know where its going and what its doing and how any given NPC will react.
Actually I have. We had a group that had about 9 regulars, and often the group might split up to manage separate tasks, or get separated through no intentional plan, so we had 2 DM’s. When this happened, the DM’s would step aside and confer, and then the group would break into two rooms until reunited. When together, the 2nd DM would help manage some of the administrative things: keeping track of hit points of monsters during a battle, make determinations on a PC’s inventory sheet, pull aside a late arriving player to update him on what he missed, etc. When the group got that big, it only made sense. There was one main DM, and the 2nd DM always deferred to him, or asked him questions if in doubt. It was a lot of fun.
You want a server wide adventure that 1 - doesn't hinge on any of the PC's {because you know they are going to change on a daily to weekly basis], 2 - includes all levels 1-20, and 3 - is somehow History making enough to cause lasting changes to the server.
Sorry I am NOT that talented ., . . . .I will admit my failings now .
I think you underestimate your talent. Let me paint a picture for you using your server as an example and see if it doesn’t spark your creativity. The “event” would be something that has upset the order of things, and has many cascading elements to it. Normally, the little world is in balance. Sure there are opposing factions that have conflicts, but they are largely offsetting and not disrupting civil society. In comes the “event” to stir the mud and cause all kinds of problems.
The Plot: (many parts of this would be unseen to the PC’s at first, but it would come together in pieces as they go through the event). The Dread Pirate Red, who ruled the largest pirate faction on the seas around Moonshae, has died. Her death left a massive power vacuum in her criminal organization, and various lieutenants and their loyal followers are now warring to claim her empire. What’s more, the treasure map which gave the safe route to her personal wealth stash, is missing. The resulting conflicts has forced large elements of the pirates on shore, and the order of things has been upset.
What’s really going on: The Dread Pirate Red was killed by a powerful necromancer to obtain her treasure map. One of Red’s recent hauls included a powerful artifact that the necromancer wants. However Red’s map was complicated, and the necromancer is having problems solving the riddles and defeating the traps Red put in place to protect the bounty. The lieutenants of Red know of how and why Red was killed, and are racing each other to intercept the necromancer and claim the treasure themselves, often fighting one another along the way.
The effects and what it means for the PC’s: The trail of the necromancer’s hunt has left areas of discord all over, and the PC’s are left with the task of dealing with the effects of his hunt.
Low level: one of the first places the necromancer visited was a wooded area. He set up several camps of operation as he worked to solve the clue. His camps included summoned undead to protect him from the wildlife there. The PC’s start by dealing with agitated wildlife displaced by the camps. This wildlife has been pushed into habited areas and attacking villagers and travelers going down the road. At first the PC’s try to deal with the animals to stop the attacks. The PC’s then learn of why the animals are agitated and are sent to deal with the camps themselves, killing the undead and smashing the device that is holding them there. Treasure: animal pelts, items found on skeletons & zombies, rewards from thankful villagers and travelers.
Mid level: the warring factions of the pirates have lost many ships, and refugees have come ashore to set up camps and make a living until they can again reform and return to the sea. A local elven village has found itself between two such camps of rival factions, and the daughter of the elven leader was taken. The PC’s are called in to at first deal with pirates blocking safe routes in and out of the village, and then to try to deal with the pirates themselves, having to attack two different camps in hopes of finding the taken girl. Complicating matters is the disruption of the woods near the pirate camps, which includes a large group of bugbears who are mad and attacking any human it sees. Treasure: items found on pirates, items found on bugbears, reward from the village for the safe return of the girl.
High level: the necromancer is close to finding his prize, but not there yet. A druid has put out word that he is hiring powerful adventurers to help him solve a problem. An ancient shrine, a sacred site once home to Larue, has been disturbed by dark magic. The druid is offering a powerful magic item as a reward to a group of souls who will purge this shrine of the fell magic which has corrupted it.
Turns out that Red hid the key (a powerful magical key) somewhere in the crypts beneath the shrine. The crypts once contained the honored dead of Larue’s loyal worshipers, but now they have been animated and turned into powerful undead by the necromancer to protect him while he searches. The PC’s who take up the druid’s quest will have to face two lieutenants separately along the way, then finally the necromancer and his powerful minions. If they seek the key themselves, they’ll have to deal with the traps and spirits in the crypts. Note the remote area has many powerful creatures and the presence of powerful dark magic will agitate normally reserved creatures living near the shrine. Treasure: items on the lieutenants, items on the animated dead, items on the necromancer, reward from the druid (if he doesn’t have to do the dirty work himself).
End game: The lower PC’s (and some villagers if needed), are able to clear the undead that were bothering the wildlife. The animals retreat back into their home, and order is restored. The mid level PC’s (and some elves if needed) are able to defeat the pirates, driving them away, and restoring order to the woods allowing the bugbears to calm down. The high level PC’s (along with the Druid if needed) are able to cleanse the shrine of the necromancer (either driving him off or killing him).
Epilogue: A third lieutenant, Red’s most trusted, already knew the location of the key, and removed it before the necromancer could get there. He used the key to claim the loot, and bought the loyalty of the rest of the pirates and replaced the lost ships. A new Dread Pirate is born, and order is returned.
So there you have it, a plot for all levels, with different groups managing different elements of the plot. Took me about 30 minutes to come up with it during my morning commute, and about an hour to write it up for you. You can complicate or simplify portions to meet the needs of the players. The idea is simple: take your orderly world and drop something into it which disrupts the order, and then imagine the cascading ripples of that disruption to dream up opportunities for the PC’s to solve. The event doesn’t have to have any permanent effect; that is up to you.
You can script pieces of it, chain it together, and make it a permanent feature of the server when you’re done, or do it all DM run by declaring different nights oriented for different levels. I envisioned doing it in episodes one per week, so about 4 different plots to get to conclusion. You could maybe have a banquet at the end where bards share the lore of the event and PC’s get to share their personal tales with one another. If you want to put in permanent effects, little markers on the server, that’d be fun. A marker where a PC fell, a scripted lore dialogue from an NPC or two, perhaps scarring of a building. It can be as simple or involved as you like.