Some questions about Call of Cthulhu 7e's dice system

[Thaumic]

Recently some of my friends/players have expressed interest in trying out Call of Cthulhu. Up until this point, we've only ever played D&D 5e, so that's all I'm familiar with. I've done some research and am excited to try running a one-shot, but I have a few questions about some of the specifics of the system (or, really, d100-based systems in general). It should be noted that I have only read the Quick Start Guide; I'd rather not purchase the full rulebooks until I know that my players are going to enjoy the game. My questions are:

1. How are character abilities typically represented in the difficulty of a check? By this I mean: what bonuses should a character with a skill get over those without one? As an example: imagine a professor with a 70 in "Library Use" and a police detective with 40 are both searching for information. Is the fact that the professor is more likely to succeed enough? Should a GM require a Hard success from the detective but only a Regular one from the professor? Should the professor get a Bonus Die?

2. When should a Keeper call for Luck Rolls, exactly? Are there times when they should always/never be used, or is that decision completely up to the Keeper?

If anyone has any other advice for new Call of Cthulhu GMs, that would also be appreciated!

[Khedrac]

In general, if the check is a hard check it is a hard check for everyone - and that is where having a high skill is useful - it means you can usually do what you need to. I would only apply modifiers to some characters if there is a reason why one character might have an advantage/disadvantage (e.g. this is one character's home town and their background shows they know their local library very well - so give them a bonus as they are using their home library).
In general you should have most of the characters making checks for the same thing - this way if the expert rolls badly there is a decent chance that someone will succeed and the party will get what they need. Common skills like Library Use usually end up with every character having an experience check to make at the end of the adventure, and this is where the experience system kicks in - the skilled people are less likely to improve.

Luck rolls tend to be used when no other skill seems appropriate, for exmaple if a single assailant is about to shoot at the party, make luck rolls to see who gets attacked. Equally if the party completely failed to find the clue they needed under a loose floorboard with their spot hidden checks, use a luck roll to determine who puts their foot in it (literally).

The main advice for new CoC Keepers is "don't try to kill the characters" - CoC is a very lethal system, so characters are quite likely to die anyway - most monsters are way tougher than the party and there is no need (or point) is playing to kill the characters. Instead, play to drive the characters insane - it's more fun for everyone.

Next, don't worry about "atmosphere" - every time I have an enjoyable CoC game there tends to be a lot of laughter during the session - playing a horror game does not mean you cannot have fun (if you are not having fun, why are you playing?); suhc games often seem very silly, but that is actually part of a natural human reaction of how to deal with very horrific situations. You know you are GMing right when the players are laughing at their character going insane.

Never play CoC by candle-light - I was persuaded to try that once at school, and it makes the pencil markings on the character sheets (which are subject to a lot of erasing and re-writing) very hard to read...

(You know you are old when everyone in your CoC group pulls out reading glasses or similar, and the only new dice that get "ooh"s form everyone are the special large ones that are easier to read.)

[Anonymouswizard]

1. How are character abilities typically represented in the difficulty of a check? By this I mean: what bonuses should a character with a skill get over those without one? As an example: imagine a professor with a 70 in "Library Use" and a police detective with 40 are both searching for information. Is the fact that the professor is more likely to succeed enough? Should a GM require a Hard success from the detective but only a Regular one from the professor? Should the professor get a Bonus Die?

As a general rule in percentile systems having a higher chance is a big enough bonus in and off itself, especially as in many it increases the chance of a better result (such as Eclipse Phase's 'criticals on doubles' rule).

Remember that, except for a handful of exceptions (looking at Eclipse Phase again) percentile systems work on the idea that ratings begin at 1 and extend to 100, with the rating being your chance of succeeding an average difficulty task while under pressure. So the professor is already almost twice as likely to succeed, before we take modifiers into account (don't know how CoC7 does it, but in 6e with a bit of effort to get a lot of time you could push effective skill values up to the >100% mark, which is obviously easier with skills you're good at).

[Mordar]

If anyone has any other advice for new Call of Cthulhu GMs, that would also be appreciated!

Make sure everyone is on the same page...that being "CoC is an investigative mystery game, and your characters are investigators...not troubleshooters, bada$$ action heroes or gods-in-mortal clothing". Then find ways to incorporate all the kinds of investigation...sleuthing, research, social interaction (and all the kinds of social interaction...fast talk, schmooze, intimidate)...particularly early on in the process so the players learn that there are tons of ways they can learn important information.

Other than that, I suggest starting with some of the nice easy sample scenarios before trying to either create something on your own or diving into one of the many (some extremely good!) world spanning campaigns they have published.

Personal bias: If you (generic you, not Thaumic you) play CoC as a meatgrinder/mindgrinder where you measure success by how many investigators die/go bonkers, please don't. Play Paranoia instead. CoC deserves better.

- M

[Anonymouswizard]

"CoC is an investigative mystery game, and your characters are investigators...not troubleshooters...

CoC investigators tend to have much longer lives than troubleshooters. I'm not sure why, the thermonuclear hand grenades we issue to all troubleshooters should take care of almost any threat.

I'm agreeing with you in general though. Horror games aren't good as meatgrinders, they're good when you're playing with the knowledge you're weak and don't know anywhere near everything. A good GM will make sure that players who come up with a decent plan to survive will live to fight another day, while a good player will tend to avoid getting into deadly situations as much as possible anyway. Flavour to taste with limited supplies, sanity meters (Unknown Armies and Nemesis having the best insanity system of any horror game*), and eldritch abominations.

Also, while people tend to think of Call of Cthulhu when they bring up mad characters, Unknown Armies is the best game out there for character madness. Lots of players will willingly take madness for power or try to make their life more like an archetype for power (which is also going to slowly drive you mad), losing insanity is hard, and every time you roll for insanity you will end up more insane or detached (and get too detached and you lose those tasty Avatar powers you paid fifty or more skill points for). When played as intended there's a lot of balancing insanity, you don't want to have too detachment, but you also don't want too much, and unless you snap into being an Adept (who are mad enough to warp reality) filling a madness meter is pretty bad news. Don't try to snap into an Adept when you already have Adept powers, that leads to permanent maximum insanity in Unnatural, Violence, Helplessness, Self, and the one I always forget, and that leads to a character who either very quickly can't meaningfully interact with anybody (on the plus side you can warp reality in two areas!)

* The trick is that you have two tracks for various triggers, insanity and detachment (Failed and Hardened in-game). Different values in each of these tracks will end up with you having different types of madness. Generally insanity gives you something like your standard game madnesses, but slowly increasing, while detachment makes it harder to gain madness but makes you less able to deal with normal people.

[Thaumic]

Thanks everyone, very informative!

Other than that, I suggest starting with some of the nice easy sample scenarios before trying to either create something on your own or diving into one of the many (some extremely good!) world spanning campaigns they have published.

Yeah, I'm going to be running the simple scenario included in the Quick Start Rules. In case this does become a regular thing for my group, is there a specific published campaign you would reccomend? (I'm doubtful of my ability to homebrew a mystery-based campaign like CoC)

[Mordar]

Thanks everyone, very informative!

Yeah, I'm going to be running the simple scenario included in the Quick Start Rules. In case this does become a regular thing for my group, is there a specific published campaign you would reccomend? (I'm doubtful of my ability to homebrew a mystery-based campaign like CoC)

Got to be Masks of Nyarlathotep. Maybe the best of all time. I also liked Shadows of Yog-Sothoth, but not sure everyone did.

Either will require updating to 7th edition, but the 7th edition stuff has a guide for doing so...

- M