I’m currently prepping a Trail 0f Cthulhu Campaign. Usually I opt to run Mythos based campaigns as one-shots or “monster of the week” style campaigns, but this time I chose to go for a multi-faction conflict game in which the mythos is involved in it’s own internecine struggles for scarce resources and the investigators must choose the lesser evil, oppose all comers, play the sides off against one another, or anything else they think of.
I’ve set up this sort of campaign before, but it’s been fairly labor intensive, and that doesn’t fit well with my prep schedule, so I’m outlining a step by step process to make it easier to work on this type of campaign without endless paperwork.
Basic Campaign Concept Design
Just like normal, before everything else I need to outline briefly what’s going on in the campaign; system, players, flavor, pitch, etc.. This is a pretty standard step, so I’m not going to spend too much time on it, just knock it out move on.
For my game, I want a fairly standard Mythos game. I’m using the Trail of Cthulhu rules from Pelgrane Press  (at which I highly recommend any mythos fan take a look)and am using mostly purist options (as opposed to the pulp-style options). I have a pair of players already slated and have a few more in mind to pull in if available. My pitch is pretty much the internecine struggle amongst mythos factions mentioned earlier.
Just Who Are These Factions?
Next I need to know who my factions are. Not every group has to be listed, just the notable ones, but any details that can be quickly noted are useful, especially on things like roster, and disposition between factions.
For my game, I had a few Mythos entities in mind based on my players, and a few ideas of my own I wanted to incorporate. One of the really neat things about Trail of Cthulhu is that they encourage GMs to rethink individual Mythos entities or even the nature of the Mythos itself and include several re-imaginings for each major being they cover. Mentioning this is both praise for a novel idea, and justification for why not everything that follows is cannon. I jotted a listing of things I wanted to include and discovered that a fair number of them had a common ground in being based on or otherwise associated with the moon, so I tossed out a web diagram starting with the moon as central and working out. Pouring over the Trail of Cthulhu rulebook, the Call of Cthulhu 5.6 rules, and the Encyclopedia Cthulhiana 2nd edition  for clues and additional material, I felt like a mythos researcher hunched over musty tomes searching for sanity blasting secrets. I ended up with Bast, Golgoroth, and Mormo in lead roles, with Golgoroth and Mormo indifferent to one another and Bast as a rival to both. Human cultists, cannibal cultists, the cats of Earth and Ulthar, moon beasts, totem beasts, shantaks and hounds of Tindalos fill the roles of servitor races, and Shub Niggurath, Azathoth, Quachil Uttaus, and Nyarlathotep and various servitors taking a peripheral role. Interestingly enough, Mormo and her ally Shub Niggurath both take aspects of femininity and fertility, so that should make an interesting theme for the campaign, as should the contrast of Bast, the goddess of pleasure and Golgoroth, the god of sensation. The only non-cult human agency is the police, whose goals are mainly to keep other human agencies in check.
What Are They Up To?
Taking a look at the factions, I need to decide on which ones I care about enough to work into the story, and which are merely there as resource draws and bit players. From there, I need to work out brief general plan outlines for the major players. The bit players don’t get goals of their own (in this story). If they did, they wouldn’t be bit players.
Looking at my setup, it’s obvious that Bast, Golgoroth, and Mormo need plans, but no one else does. The police have a plan but it consists of “cause trouble for any other faction with a high enough profile” so it doesn’t warrant writing down, and while other players may show up as part of, or foiling the plans of the major players, they don’t have their own goals for the purpose of my campaign.
Bast is a fairly benevolent great old one (as far as that goes) but has little power on Earth, and her major worship centers in Bubastis and Atlantis have been wiped out, leaving only the cats of Ulthar, in the moon’s dreamlands. Bast’s plans then are to gather a worshipper base of humans and earthly cats, find a temple, expand it, and perform the great rite that will summon an avatar.
Golgoroth Dwells on the moon and communicates with his followers via totem beasts, which require cannibalistic rites to summon. His worshippers drink blood-mead to create a mental link between themselves and their god before engaging in brutal orgies of violence and sensation. Golgoroth’s plans are to gain enough worshippers to establish cults in several magically significant locations and summon a handful of totem beasts and a shantak as his representative in each. From there, a huge ritual must be prepared and cast to bring Golgoroth to Earth for a night of carnage and orgy which will ruin large swaths of the city.
Mormo has the largest servitor base of the three major players, including humans, supernatural creatures such as vampire, ghouls and werewolves, and mythos creatures including moon beasts and hounds of Tindalos. She has loose alliances with Azathoth (and through him, Nyarlathotep) and Shub Niggurath (though which she gains access to dholes, dark young, and satyrs. She has many aspects including the three sorrows, and various goddesses of ancient religions. Because Mormo is so fragmented, she pursues many small goals at once, advancing her worship in several forms, promoting the cause of her worshipers, and advancing women’s right. Her big goal will be to use her human and supernatural support base to elect several followers to major local offices. Mormo will be fun to use because many of her small goals are insignificant, and the fight for women’s rights is noble, but many of her servitors and plans are dangerous on the small scale, leading to an interesting moral dilemma.
Now I know enough to plot out a rough timeline for each plan, showing where each group will be (barring interference) in relation to one another. This provides a skeleton on which the campaign’s adventures will hang. It’s well within the PC’s power to fracture some bones and drastically alter the timeline though, so spending more time on this than roughly sketching some stuff onto a piece of paper would be misguided.
It’s Adventure Time !
Now that the skeleton is in place, it’s easy to find where the PCs are and write an adventure that’s appropriate to what the various factions are currently doing. Mission accomplished!