1 A plot to carry out some harmful, wrongful, or subversive illegal act, especially a political plot
2 A secret agreement between two or more people to perform an unlawful act
3 A group of conspirators banded together to achieve some harmful or illegal purpose
4 A joining or acting together, as if by sinister design
Conspiracy theorists are people who believe the government is secretly controlled by power brokers in flagrant violation of the constitution. They believe these power brokers control everything we see on the TV, are able to read on the internet, what laws get passed and more.
1. Conspiracies Must Be At Least, In Part, Secret Even if "publicly known," there should be some part of the conspiracy that isn't known.
Even though the Free Masons are a publicly known organization, it doesn't mean the public at large knows the full extent of its activities or ambitions.
What if the upper echelons of their organization sought to covertly control the government?
What if the Skull and Crossbones really do control the US President to shape national and international policy?
A plot of which everyone knows all the particulars will likely fail because, by definition, it is harmful to others. People wouldn't sit around and let something terrible take place, they'd do something to stop it. If the right people knew of the plots to assassinate President Kennedy, someone would have stopped it.
When determining what is secret and what is well-known by the public at large about a conspiracy, think about what means they will and will not go to keep what is secret a secret.
For instance, a conspiracy dedicated to nonviolence may simply imprison those that find out about it. Or they might swear them to secrecy about what they've seen or heard.
2. Determine The Conspiracy's Reach
A conspiracy can contain as many or as few people as you desire.
Keep in mind, the more wide-reaching the conspiracy is, the more likely it is to be found out.
A conspiracy of two people can hide better than a conspiracy consisting of dozens or more people.
A conspiracy might be as simple as replacing the sheriff in a backwater town, blackmailing a local religious official for financial gain, or overthrowing the gods themselves.
3. Multiple Conspiracies May Have The Same Goal
Create multiple conspiracies that have the same goal but differ in significant ways.
For example, beholders and mind flayers might be conspiring to control the government but each faction has different reasons.
When setting up multiple conspiracies, determine the goals and leadership of each and whether or not they work together on some level or not.
Also determine if they would be hostile to the other conspiracies if they found out about them. If they would become allies, how would they work together?
4. Conspiracies May Have Something They Wish To Protect
If the conspiracy is protecting something, determine what it is and to what means they will go to protect it.
Also, determine the consequences of the fallout if and when the conspiracy is discovered. They could be different than what the conspirators imagine.
If the government conspires against the people from the presence of aliens, it could be to protect them from widespread panic and the fallout from such.
What happens to people who try to expose the government's secrets to the public?
Do whistle blowers mysteriously disappear or are they discredited by officials?
5. Conspiracies Must Be Dangerous
The danger might not always be physical, in the sense of hurting others. Though it can be, if necessary.
Determine who is going to be hurt and exactly how if the conspiracy succeeds. Also, determine the unforeseen fallout if the conspiracy succeeds.
Conspiracies must also be dangerous to people finding out about it. The conspirators could fight and kill those who know about it or simply disappear, never to be heard from again. They could be executed as a traitor to the state.
A more insidious method might be to "prove" to the people who found out about the conspiracy that they were wrong and get them to recant.
Another method is recruitment. If they people who discovered the conspiracy are corruptible or swayable, they could be granted entrance into the conspiracy, which is a danger to their morality.
6. Conspirators Might "Switch Sides" If Shown Their Error
Just because conspirators are dedicated to their cause, doesn't mean they can't change their minds or tactics. Perhaps the PCs can persuade them to look at other options, or even the other side.
When writing an NPC, determine what new facts or circumstances might cause them to change their mind or allow the status quo to continue.
7. Conspiracies, If Successful, Must Be A "Game Changer"
Determine what the conspiracy will do if it's successful. Bigger stakes mean better stories.
Will it rewrite the rules of magic? Will it unleash an ancient demon from another dimension onto the unsuspecting public?
Whatever the "end game" is, it must change things forever.
8. Conspiracies Might Be Only In The Mind
Just because your players see conspiracies doesn't mean they exist.
Alternatively, a conspiracy might be different than what the PCs see or think. This is your chance to add twists to the story.
The conspiracy might actually be much simpler or much more complex.
Also, what seems to be a conspiracy might be just circumstantial evidence pointing to collusion when none such exists.
9. Conspiracies Should Be Fun
Don't stress if your players don't pick up on all the conspiracies that are in the game or see them where they aren't.
Some things they may simply write off as mysterious. It's all a part of the fun of the game.