Running a Conspiracy Horror Campaign in Trail of Cthulhu

brochurevampConspiracy Horror in Trail of Cthulhu

by Justin Farquhar

These guidelines will help you to incorporate a thoroughly conspiratorial feel into your Trail of Cthulhu campaign. They make use of conspiracy mechanics found in Night’s Black Agents, so you will need a copy of the Night’s Black Agents (NBA) core rulebook as well as your Trail of Cthulhu (ToC) rulebook. If your intention is to run a thriller – especially a modern thriller – using the Cthulhu Mythos, it is recommended that you instead use The Dunwich Sanction build for Night’s Black Agents (NBA, p195).

What is Conspiracy Horror?

In fiction of all sorts, the existence of a persistent and organised group of antagonists plotting against the interests of civilised humanity is a classic device that forms the basis of the story arc. True conspiracy fiction however, brings distrust and paranoia to the forefront – the conspiracy has infiltrated society and the protagonists don’t know who they can trust. In horror, a conspiracy can help to evoke the sense of a menacing reality that lies beneath the veneer of mundanity. Lovecraft used this device in many stories, notably The Shadow Over Innsmouth, The Whisperer in Darkness, The Call of Cthulhu and The Haunter of the Dark. Examples of conspiracy horror movies include Invasion of the Body Snatchers, Rosemary’s Baby, The Wicker Man and Jacob’s Ladder.

Almost every Trail of Cthulhu and Call of Cthulhu campaign involves a plot by cultists or mythos entities. However, no matter how complex or ambitious the plot is, these don’t usually constitute conspiracy horror in the truest sense. True conspiracy horror brings the specific, features of conspiracy to the foreground – secretiveness, distrust, betrayal, disguised menace and active opposition. In a true conspiracy horror campaign for Trail of Cthulhu, there must not only be a group of antagonists working to bring about the return of the Great Old Ones (or whatever), they need to have infiltrated society, or the Investigators’ organisation, so that the Investigators don’t know who to trust. And they need to have the power to act against the Investigators. If the characteristic mood of a Lovecraftian horror campaign is cosmic horror, the mood of Lovecraftian conspiracy horror should be cosmic horror plus paranoia.
Campaign Design

In terms of the broad structure of your campaign Trail of Cthulhu campaign, refer to The Continuing Conspiracy: Campaign design (ToC, p199). The equivalent advice in Night’s Black Agents – The Thriller Skeleton (NBA, p184) and The Campaign Story (NBA, p193) – is also well worth referring to, particularly with regard to antagonist reactions. This advice, however, is tailored for the thriller genre, and is high on action and early shocks. Unless perhaps you are running a very Pulpy game, it will need to be toned down – action should be more low-key, the horror should build more slowly and, particularly if your campaign has a strong Purist feel to it, the Endgame should confront the Investigators with a climax of cosmic horror, with undermined Drives, Pillars of Sanity or complete Anagnorisis for one or more of them.

Campaign Frame

Some campaign frames are particularly suitable for conspiracy horror:

Armitage Inquiry

In Pulp mode, this could be a globetrotting battle against agents of the mythos. In Purist mode, the focus might be on intrigue within the corridors of the Miskatonic University itself (how high does it go?). Agents of the mi-go are almost certainly stalking Albert Wilmarth at the University; the Witch Cult is active in Arkham and who knows what forces may be trying to seize the dark knowledge kept in the Miskatonic Library? See ToC, p206 for more details.

Bookhounds of London

Think of exclusive and secretive societies and hermetic lodges in London high society and dingy, claustrophobic, cult-dominated communities in the Severn Valley. One challenge might be motivating typically selfish and cowardly Bookhounds to tackle a larger conspiracy. See ToC, p209 for more details.


The powerlessness, alienation and paranoia of institutionalisation combined with the conspiring of the authorities and uncertainty about whether the Investigators are just crazy, give this great potential as the basis of a conspiracy campaign. This campaign frame by Robin Laws is available free here.

Mythos Detectives

Having the resources and the politics of law enforcement on their side – and the possibility of its corruption – makes this an excellent choice for a conspiracy campaign. The influence of hidden hands within society’s institutions of governance, including the Investigator’s own department, would be a powerful way to create a sense of intimidation and paranoia. See Arkham Detective Tales, p6.

Project Covenant

This is a perfect campaign frame for a conspiracy game, with the Investigators part of a secret plot within government agencies. This necessitates secrecy and gives them access to classified information and exposes them to potential corruption within their own agencies. Emphasis could be on investigations within US territory, conspiracies within US institutions or far ranging secret missions. See ToC, p207; and find the Michael Dauman expansion of this campaign frame here.

Moon Dust Men

With black helicopters, men in black, and other shadowy government forces, this is another ideal set-up for a conspiracy campaign this time with a strong X-Files feel. This is detailed in the sixth instalment of Ken Writes About Stuff.


Some organisations and mythos races lend themselves better to effective conspiracy horror than others. Whether those who dominate the conspiracy are cult members or are a group of mythos entities they will need to be capable of organisation; they will probably have some sort of hierarchy; they will need rationality of some kind (no matter how alien), a degree of understanding of human beings, lines of communication, access to money and other resources and they will need some reason to conspire against humanity in the first place.  Examples include:

Black Dragon Society

This group could certainly extend covert influence through East Asia and further afield. Their secrecy and infiltration of commerce and politics would make them a good candidate for a pulp conspiracy campaign.

Brotherhood of the Yellow Sign

In The Whisperer in Darkness, Henry Akeley (who is probably being impersonated by the mi-go at the time) blames a secret organisation devoted to Hastur and the Yellow Sign responsible for hunting down the mi-go (and tampering with Wilmarth’s mail). The Repairer of Reputations by Robert Chambers describes a national conspiracy (or at least the belief in one) bearing the Yellow Sign and preparing to seize power on behalf of the King in Yellow.

Cult of Cthulhu

While this is really a number of essentially independent sects, rather than a unified organisation, they share an ancient heritage and a common interest. Probably the most organised of these groups is the sea-farer’s cult found in ports across the world, which, in The Call of Cthulhu, conspired to murder Professor Angell in Providence, because of what he had discovered. Just how far do their tentacles reach?

Esoteric Order of Dagon

The EOD controlled the town of Innsmouth for 80 years, with the raid by government agents in early 1928 being the formative event of Project Covenant (above). A pre-raid campaign could focus on initial investigation of the town’s unnatural corruption, while after the raid, the focus could be on investigation of surviving outposts, or other contaminated communities. Could other powers be conspiring to acquire artefacts captured in the raid?

Mi-Go Agents

The Whisperer in Darkness describes a secret network in Vermont, capable of spying and intercepting mail, and sometimes resorting to violent intimidation. Mi-go themselves can mimic human speech, may be able to transplant brains from one person to another or take a semblance of human form with prosthetic body parts or hyper-advanced surgery. In terms of a mythos conspiracy game, this is gold dust.

Serpent Folk

Humanoid reptiles that can take human appearance would be great antagonists in a conspiracy game. And the overlap with the modern ‘reptoid’ meme is compelling. What if David Icke was right and the world really was led by an elite cabal of shapeshifting reptiles?

Starry Wisdom Sect

A secretive urban cult that can attract and corrupt the rich and powerful is ideal for a conspiracy campaign. What sort of political corruption allowed this murderous cult to flee from Rhode Island when faced by an angry mob in 1877? Did the cult simply go underground under the leadership of Enoch Bowen’s daughter Asenath? In Strange Eons, Robert Bloch refers to a branch of this sect in LA in the 1920’s and 30’s with likely influential members in Hollywood, law enforcement or government.

Yithian Agents

The knowledge and technology of the Yithians is beyond human understanding. They are highly intelligent, secretive and essentially indifferent to human concerns. They are served by human agents that may be embedded in society at any level and any location. They may at times seek to influence events in ways that are antithetical to the interests of humanity. They would make good antagonists in a conspiracy game, but their motivations should be marked by cold indifference to human concerns rather than a desire for power or destruction.

ToC, p160 has more detail on many of these organisations.

Conspiratorial Considerations

Most of the advice in Conspiratorial Considerations in NBA, p156 applies equally to a mythos conspiracy.

‘Mythos Need’
Mythos conspiracies don’t generally seek power over humanity for its own sake – they seek to bring the return of their favourite Great Old One, to rid mankind of the scourge of reason and sanity, mineral resources found only on this planet, information about human life in the 20th century, or to alter the course of evolution or history for some alien purpose. Alternatively they might be trapped on the earth and simply be attempting to protect themselves from human interference. This requirement lies behind all other details of the conspiracy – this is why they are interacting with human society in the first place.

As in Night’s Black Agents, this consideration concerns your conspiracy’s intentions at a political level.

Parallel State: Mythos conspiracies are likely to be less dependent on humanity than vampire conspiracies, but mi-go for example might need to parasitise human societies in order to harvest brains, Yithians might need to do so in order to gather research data, the Starry Wisdom sect may do so in order to maintain a regular supply of sacrificial victims.

Replacement State: Does the conspiracy seek to overthrow the current regime and replace it? This idea doesn’t come up often in Lovecraftian literature – some cult devotees might see the return of their ‘god’ as a type of replacement state. And in The Repairer of Reputations, Hildred Castaigne seeks to do this, establishing himself as regent and representative of the King in Yellow.

Anti-State: This describes the intentions of those entities and nihilistic cults that seek to wreak madness upon the earth or bring civilisation to an end with the return of the Great Old Ones.

Indifferent: The organisation or mythos race may be indifferent to the human world, and seek to influence it only in so far as it is necessary to fulfil its Mythos Need (above) – it may be neither dependent on nor hostile to the state, as long as it doesn’t interfere with its earthly operations.

Does the conspiracy have another group or conspiracy that opposes it (as the mi-go and Brotherhood of the Yellow Sign might)? Is there rivalry or open hostility between two or more branches of the conspiracy? Investigators might try to exploit such a situation.

Modus operandi
In order to fulfil its secret agenda, a conspiracy will have had to spread its influence through society. What methods does it use? Blackmail, bribery and threats? Assassination? Mind control? Alien parasitic infection? Prosthetic human bodies? Shapeshifting magic?

Does the conspiracy operate primarily in the higher echelons of power or ordinary farming folk or among university academics? Where is its power focussed?

Lines of communication
Communications technology in the 1930s was far slower than the modern era. How do the various components of the conspiracy communicate with one another? Letter? Telegram? Pigeon post? Where do they access these services? A cannibal cult in the Himalayas might have difficulty getting access to telegraph equipment. Do they use codes? Do they use magical means – summoned servitor races, telepathy, hyperspace gates? As always, however, avoid letting drama be trumped by pedantic details.

Conspiracy Design Tools


The Conspyramid tool (NBA, p157) is an excellent tool for defining the power structure of your conspiracy and for defining a flexible structure for the campaign itself, with a clear beginning, middle and end.

Adversary Map

This is the players’ map of the conspiracy structure. The rules for this can be found in Night’s Black Agents, p113. Relevant spends for uncovering an adversary map in Trail of Cthulhu are Anthropology and Oral History in place of Human Terrain and Traffic Analysis.


While a different name might be more appropriate in a mythos conspiracy game (‘Reaction Pyramid’ perhaps), this is another useful tool from Night’s Black Agents (p189) that can be readily adapted. The Vampyramid suggests options for an escalating series of antagonist reactions in response to the players’ investigations and assaults, with the nature of these reactions dependent on campaign style and previous actions.

Obviously you’ll need to substitute the suggested vampiric agents with appropriate agents or alien entities from your own campaign. And some steps require a slightly different interpretation from Night’s Black Agents:

Row One – Frame Agent: The targeted Investigator might be framed for a crime or tarnished with allegations of Bolshevism or something similar. Their Credit Rating ability is reduced by 2. 1 point can be recovered if they can clear their name.

Row One – Shadow Investigator: This is a contest of Shadowing.

Row One – Shadow Source: The effect may be to prevent the Source of Stability from refreshing Stability. Restoring them to a normal state is a difficulty 4 Psychoanalysis test (Psychological Triage).

Row Two – Threaten safety: This is a threat to a location that the Investigator had considered safe, for example, they find their study ransacked. It’s possible that important possessions could be stolen. In Trail of Cthulhu there is no direct mechanical effect.

Row Four – Kill Solace: The conspiracy kills one or more of the Investigator’s Sources of Stability in front of them.

Row Five – Lure Agent: Substitute with Reveal Awful Truth – the conspiracy captures or tricks the Investigators, exposing them to one or more Awful Truth, attacking their Drives and/or Pillars of Sanity.

Row Six – Destruction: As with ‘Reveal Awful Truth’ above, and especially in a Purist campaign, this final assault may include or take the form of awful revelations that destroy Investigator sanity: Anagnorisis, or destroyed Drives or Pillars of Sanity for at least one Investigator.

Conspiratorial Components

As with vampire conspiracies (NBA, p159), there are certain components that most mythos Conspyramids will need:

Funding Sources

It may not have to control a bank or launder money for organised crime, but depending on the level of influence of your conspiracy, it will need some way of funding its activities. Drugs? Smuggling? Legitimate businesses? Donations from cult members? Many mythos conspiracies have outer circles or puppet religious sects that function as shell organisations – providing a semi-legitimate face for funding and recruitment.

Protection sources

How does the conspiracy at large protect itself when threatened? If threats and violence are used, is this carried out by cult members, converted police officials, members of a controlling mythos race or summoned servitors? If they use blackmail, who does it and how do they get the compromising information?

‘Mythos Need’ Sources

If a cult requires a steady supply of human sacrifices or brains, where does it source them? Cultist volunteers? Abductions? If it needs to protect a colony, who defends or hides it?

Poaching Thriller Mechanics from Night’s Black Agents

Keepers running games that centre on law enforcement, government agencies or military personnel may find it appropriate to incorporate mechanics from Night’s Black Agents with an emphasis on action and gun-play. Note however, that introducing too many such options may be at the expense of the sense of Lovecraftian horror. Especially careful consideration should be given before using these options in a Purist game. If you choose to do this – unless you want a very pulpy, high-action feel – it is recommended that you limit these mechanics to:

  • Thriller Chases (NBA, p53)
  • Thriller Chase rules – DUST mode only (NBA, p56)
  • Thriller Combat rules – DUST mode only (NBA, p70)


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