Everybody roll "Spot Hidden".
(sound of dice rolling, a few gasps and hoots as players react to their luck)
Those of you who succeeded see something horrifying and otherworldly that drives you crazy. You attack those who failed the roll.
Basic Information
Call of Cthulhu is a role-playing game set in the Cthulhu Mythos. It draws upon the works of H.P. Lovecraft and other authors who added to his shared universe. The game is published by Chaosium, Inc, with the primary author credits going to Sandy Peterson and Lynn Willis. Like other Chaosium products, CoC is driven by the Basic Roleplay mechanic - a non-levelling, class agnostic system using percentile dice.
Player Characters are investigators into the paranormal, often ordinary folks who became entangled in something much larger than mundane reality. The game is primarily Cosmic Horror, with some flavor drawn from the Detective Genre and the era of the 1920s.
The game features a Sanity Trait, and rules governing mental health. Typically, the more you piece together of the big picture (or the current mystery), the less stable you become. In Call of Cthulhu, it's quite common for characters to be retired early because they went crazy, or came so close to going crazy that they won't survive a second adventure. Likewise, it's also pretty common for characters to meet horrible messy doom. That said, one way the game does deviate a little from the Lovecraftian canon is in the ability for characters to (sometimes) fight back (if they're really luck, and the situation is just right) and defeat the (smaller and less alien) monsters of the Cthulhu Mythos. Yeah, going toe-to-toe with an Eldritch Abomination is still suicide and madness, but it's conceivable you might take down one a Deep One with a chainsaw or tommy gun and live to tell the tale. From a certain point of view, that's a pretty big break from how ol' Howard Phillips wrote it. Most of his protagonists run for their lives or faint dead away, although other, later Mythos collaborators have different approaches ranging as far as the almost optimistic work of Brian Lumley. HPL was not the most manly of men and his protagonists tend to follow suit, whilst by contrast the few intrusions of the mythos into the works of Robert Howard tend to be met with a fist/sword/six-shooter to roughly where the face ought to be - and most players will probably prefer a more robust persona over the trembling aesthetes of the original source. The game - albeit sometimes with spin-off versions - is supportive of most of this. Still, even given lack of power curve implied by a class-and-level free system there is a distinct feeling of decline written into the game: PCs can achieve limited victories, but will never become superheroes and may end up in many ways worse off than when they started.
Partly as a result of that inbuilt expectation, the game lends itself well to "one-shots" - single adventures with characters designed specifically for that scenario who are not intended to be used over a prolonged campaign. Survivors might appear in a sequel, or, in the event of a TPK, one adventure may have been the "twenty minutes with jerks" for another, but in general the players are not expected to get attached. This can also lead into the sort of secret agendas and hidden identities that often poison a prolonged campaign. Incidentally, done correctly it can also make for very theatrical play with each adventure having a very filmic feel to it1.
Character Creation utilizes random die rolls. Characters are primarily skill-based, and successful skill use can raise skills. (Unsuccessful use tends to end badly). The in-play mechanics are percentile-based, and can sometimes feel arbitrary and unforgiving. A good GM will emphasize and play up those traits, as it fits the subject matter quite nicely. In Lovecraft's tales, mankind was far from the pinnacle of creation. We're just an afterthought, perhaps no more than a bit of foodstuff for the ancient horrors that will one day reclaim the earth. Mankind's survival thus far has been mostly luck, and our days are numbered.
Cthulhu adventures often come with detailed player hand-outs, from scribbled pages of incomprehensible notes to fancy fake passports for the characters. There's an immersive quality as piece together the clues yourself. The game remembers that it is horror, and tries hard to psych out the players. When it succeeds, the results are memorable.
The default setting of Cthulhu is the 1920s, but recent versions of the core book also include rules and background information for a game set in the 1890s or Modern Day. Many of the published materials cover the towns of Lovecraft Country, such as Arkham, Dunwich, Kingsport, and Innsmouth. Other source books cover Dark Ages Europe, Modern Day Japan, and Kenya between the World Wars. Variations on the setting abound, from Delta Green to Trail of Cthulhu, and there have even been some crossover products for other systems (Deadlands and Paranoia, possibly others). For a really divergent take on the setting, see CthulhuTech.
Tropes Appropriate To Cthulhu:
Go Mad From The Revelation is all you'll ever need. :)
You'll find additional lists of tropes pertaining to the game and setting on our Cthulhu Mythos and Cosmic Horror pages.
Magic is Evil - or at least incompatible with being a functioning human.
We live in a fishbowl
Sources
Game and Story Use
- The Cthulhu Mythos can be readily transplanted into other settings. Insert a few cultists, a slumbering alien god, and season with insanity to taste.
- Conversely, the CoC rules run just fine without the Mythos … or without any supernatural elements at all and make a passable set of "BRP Modern" rules.