Having just talked about one-shots, I thought it would be a good time to talk about one-shot trilogies. It's quite the seemingly contradictory term, however it's a nice framework available to Dungeon Masters. The idea here is simple. We've all seen movies that get extended into a trilogy. Each movie, ideally, should be a complete story on its own but taken together add up to something bigger. We can do the same thing in our games. It's really more of a three-shot, but “one-shot trilogy” is how I first heard it introduced and it stuck.
I've found that this kind of setup works best if each session is a full complete story. It's also what makes it a one-shot trilogy and not a super mini campaign. Mini campaigns can be a lot of fun too, but they are a different method and less restrictive. That's a nice thing, but sometimes more constraints help bring out the best work. The time spent for introductions before jumping into the meat of things decreases after the first section, since we'd have set up the settings and backstory by then and will be adding to it, but we'll still expect to have a complete story.
In my rather short career as a Dungeon Master I've seen quite a few of these kinds of games. One of my earliest Dungeon Masters liked this setup because it meant that you could have a more involved story than a one-shot, but still had much better odds of finishing the whole story. It also let him play around with everything and come up with new concepts each time, which he liked a lot.
Seeing these play out, and seeing them happen a few times without having a specific term applied, there were typically some rough structures that came about. I think they are helpful to consider and think about, but they are also vague enough that they allow for a lot of wiggle room.
High Level Overview of General Structure
This introduces the player characters to each other, the world, and the conflict that will be the source of the story to come by having the players directly contribute to it. Mistakes made by the players bringing about the conflict, getting dragged into events already unfolding due to luck or fate, and willingly wading into it either naively or knowingly are common starting points.
Since we still have limited time to work with, I've found that trying to get most of the information relating to the trilogy is important at this stage. The biggest challenge here tends to be still having a compelling and interesting ending that ties things together nicely but still leaves room in the next one-shot to expand. In a lot of cases the main conflict hasn't been touched but some level of closure tends to work best.
The player characters have won a great victory. Or they prevented a crushing defeat but didn't exactly win either. Regardless, there is still work to be done. Complications can occur both as a result of the ending of the previous one-shot or also as a result of actions taken here. Progress should still be made towards the end goal, otherwise it could feel like meaningless meandering, but it shouldn't be a simple journey either. I've seen it work otherwise but it's not easy.
Since we've gotten most of our information out in the previous one-shot, we can jump into the meat of the adventure. We could have held out a few important revelations but by the end of this one almost everything should be known. If there are some shocking twists planned, making sure you can count all the new bits of information needed on one hand tends to be a good sanity test. Being interesting between 2 well focused sections like this can also be a challenge. Also make sure to wrap up the complications to some degree so that they can be neatly completed closed in the ending. The solution here tends to be to make sure it directly contributes to the ending/solution in some way. In practice this also means that a complication is introduced, partially addressed, but isn't solved. There is also some room for more complications in the next section, but it should be light to keep this structure and a natural result from the events here.
It is now time to end things. This will either be a great victory, or victory won at a great cost, or a form of Pyrrhic victory for the player character's enemies (the enemy will now lose, though the players may not see the final blow). Things are wrapped up.
A large part of this often ends up writing itself. The challenge tends to be to close everything nearly. All of this is greatly contributed to by the foundation built by the previous one shots. If there is too much to close because the complications weren't properly handled, this section can be sloppy. Likewise, if we didn't manage to introduce everything previously, it may not feel like much of an earned conclusion. The pieces should be in play, can be guessed at, or aren't too much of a stretch. In other words, everything should be close by and setup. Now it's time to draw it all together and clean up. Ideally this section should be a lot of effort on the part of the players to bend things to their will.
Past 3 One-Shots
We can add more complication sections and extend this structure past 3 sections. This can work very well but doing too many complication sections can make things feel more drawn out than you'd want. It can also start to look like a regular campaign, which isn't what we are after here. The whole point of the restrictions is to give a focused and efficient story. This structure can be very refreshing after a long campaign.
All three parts don't need to involve the same characters. I've played 2 of these where all 3 one-shot's didn't share player characters. In one, an ancient evil was accidentally unleashed by the players in one-shot 1, though they got what they were after. In one-shot 2, the same characters sealed the evil but were not able to destroy it. One-shot 3 had a different set of characters years later finding a way to find where the ancient evil's prison was to destroy it, racing against a group who would seek to release it again.
In the other, an ancient necromatic evil was unleashed. The players, unable to find a permanent solution, restored the status quo. Years later, the ancient evil was guarded ever since to prevent its release. Some of the player characters were descendants of the original group. A new plan was hatched to release the evil once again and the players stopped it. Finally, hundreds of years later a method to destroy the evil was finally found. However, the player character's, some of them descendants from the characters in the previous 2 one-shots, were unable to convince the establishment of following through with this plan. What followed was a story of betrayal and manipulation to attempt to release the evil before it was finally destroyed or failing that, keeping it intact but sealed. Break in and destroy it themselves or try to convince the authorities that it should be done were the main options. Trying to play long distant relatives of previous characters can be an interesting role-play challenge. Hopefully these outlines inspire someone out there. We succeeded in stopping the plot in one-shot 2, however, I suspect it may have led to an extra one-shot to close things off before heading into the conclusion if we failed.
Instead of making more and more sessions in the same story, you can make trilogies that are connected in some way. It could be location, or it could be a common thread such as an antagonist with different plans over the centuries and millennia. Each attempt would be a vastly different plot that would take 3 one-shots to prevent. I've found that antagonists, players, locations, and items work quite well in this regard.