This makes plotting simple. The villain wants something so it acts. The PCs then react to that action, and thus conflict is born. The villain, generally, is in some way trying to change the status quo in some means to their favor. Starting a war they can use to claim territory, conquering a kingdom, unleashing hell beasts towards some other grand end, or - perhaps - just wanting to destroy the world.
The PCs, or heroes, are thus on the side of preservation. Maybe they want their own changes, but they are fighting against this change the villain is doing.
Now good or bad can be easily swapped without changing key roles. For example, in Star Wars the Rebellion is trying to change the Status Quo and Darth Vader is trying to maintain it. That doesn't make Vader the hero for how the story is shown or what the Empire is shown to be.
These simpler stories work well for RPGs because they're easy to understand. X group is the bad guys. The PCs are trying to stop them. The story of doing that is the game.
Sometimes, however, you want more complex stories.
A complex story is one where you have more than two sides. A third party is involved and it also wants things that are mutually exclusive from what the other two sides want. The more sides you add, the more complex the story.
Heist and Spy stories frequently go for this level of complexity. Done right they can be wonderful with a lot of moments where people wonder whose side various characters are even on. However, they also run the risk of confusion because in a lot of ways a Table Top Roleplaying Campaign is a collision of plot lines done on super slow motion while the audience lives weeks and months of their lives between important points.
The plotting for one is, thankfully, not significantly different in the initial stage. It is the execution where things get messy.
A Three Way Dance
At the core, a Complex Story is 3 or more parties that all want something that the other two do not want. These wants can be mutually exclusive (each side wants the maguffin, they can't all have it) or they can be separate. If going for separate wants just remember that it has to be big enough the other two groups will fight to stop it. After all, if everyone can get what they want and be happy you don't have tension, drama, or conflict. If all 3 factions want an invitation to Wonka's Chocolate Factory and there are 3 invitations they can all get one. You don't get a conflict or reason to engage each other until they arrive and find only one of them will get a chance to own the whole place.
In short you need three things:
- What does this side want?
- What are they willing to do to get it?
- Why do the other sides not want them to have it?
These three things give you the core of what drives the side. And then for each important plot point along the way you need to ask three more questions for each faction:
- When do they learn
- How do they respond?
- How fast can they respond?
Let's continue with our chocolate factory example. All three sides (A, B, and C) have the same answer to the first three questions: they want to control Wonka's Factory, they are all willing to break the law and commit high crimes to get it, and only one side can control the factory.
The story begins with the public announcement of the factory going to whomever wins a contest by showing up with a golden ticket. There is only one ticket.
Each faction acts according to how they're setup. They all learn at the same time (presumably) and can react quickly to the news. The 'wealthy' faction likely buys up all the candy to control where the ticket is. The 'sneaky' faction breaks into factories looking for the ticket that way. The 'arcane' faction summons magical creatures to help divine the location of the ticket.
There's not much conflict just yet. But you see how we have them all at play? Now you just add the first hitch. The ticket is found, not by one of the factions.
Faction A is liable to try and buy the ticket for exorbitant sums of money. Faction B is liable to try and steal the ticket. Faction C will do something with magic, maybe send a summoned demon to get it or charm the person into handing it over. But how fast does each option get there?
Does the guy with the briefcase full of cash arrive first? Does the thief? Does the demon? How fast does each faction learn about the other factions plans? Do they do something to try and stop them?
Now we have conflict.
The Hard Part
The hard part comes in two pieces here. First, your players are doing one faction so they will determine a lot of things for how they act. That is fine and good, but you can't plan for them. The other part is that until you know how the first hitch resolves you can't plan for the second one...because until that ticket arrives at the factory, the next hitch is how do the two losing factions react to losing, and what does the winning faction do to try and stay ahead?
As things move on, this can get more and more complex because tensions escalate and so do the solutions deployed. And with three groups and only one prize, any alliances are going to be short lived at best.