The Alexandrian

Posts tagged ‘gumshoe’

Eternal Lies - Will Hindmarch, Jeff Tidball, and Jeremy KellerThe effect of prolonged exposure to extreme temperatures in Trail of Cthulhu is very straight-forward: Investigators are considered to be hurt, resulting in them suffering a +1 difficulty on all tests.

The designers of Eternal Lies had a desire to make exposure to extreme heat more mechanically interesting and they introduced a rudimentary heat track. I found their treatment interesting, but wanted something a little more robust (particularly when it came to treatment and recovery). These mechanics are specifically designed for desert travel.

(They’re also not exactly “untested”, but I don’t have a series of posts called “minimally tested”, so here we go.)


0. Not suffering heat.

1. Can only make spends after first resting for 10 minutes (to gather their thoughts and spirits).

2. Difficulty of contests +1 (including hit thresholds).

3. Difficulty of tests at +1.

4. Can only make 1 spend per day and must make it in the morning after a good night’s sleep, before the day’s temperatures begin to rise.

5. Cannot make any spends.

6. Can only refresh 1 Health per day. If Heat Track would advance, it remains at 6 but character suffers 1 damage.


Desert Travel: +1 Heat track per day. Characters who traveled during the day are considered to be under extreme heat conditions for the purposes of treating heat.

Camping: Characters who take a rest from traveling by camping for one full day are considered to be in favorable conditions for the purposes of treating heat.

Oasis: An oasis or similar place of significant respite may be considered “controlled conditions” for the purposes of treating heat.


A given character can be treated for heat once per day.

First Aid/Medicine in favorable conditions to prevent advancement or reduce position on the heat track by 1.

First Aid/Medicine (difficulty 3 + heat track) in extreme heat conditions to prevent advancement or reduce position on the heat track.

First Aid 1 / Medicine 1 in controlled conditions to bring an investigator back to 0.

Trail of Cthulhu - System Cheat Sheet

(click here for PDF)

I’ve done several of these cheat sheets now, but for those who haven’t seen them before: I frequently prep cheat sheets for the RPGs I run. These summarize all the rules for the game — from basic action resolution to advanced combat options. It’s a great way to get a grip on a new system and, of course, it also provides a valuable resource at the table for both the GMs and the players. (For more information on the procedure I follow when prepping these cheat sheets, click here.)

This set of cheat sheets is for Kenneth Hite’s Trail of Cthulhu. I’ve talked about the GUMSHOE system in past, including what I consider to be its flaws and limitations. Have I been converted? Hmm… not exactly, but I’m not going to get into it here. (Partly because I want to let those thoughts finish baking before sharing them.) So why have I prepped a system cheat sheet for the game? Well, partly because Hite’s really good at what he does: The Stability/Sanity mechanics are fantastic (particularly the metagame methods of playing out long-term madness). And the method used to present the Mythos by treating it as a catalog of mysterious possibilities instead of an encyclopedia of cemented facts is just flat-out excellent and is possibly enough to recommend purchasing the core rulebook even if you never intend to play the game at all.

Trail of Cthulhu: Eternal Lies - Will Hindmarch, Jeff Tidball, and Jeremy KellerBut the major reason is Eternal Lies, a mega-campaign designed for the game by Will Hindmarch, Jeff Tidball, and Jeremy Keller. My great love for The Masks of Nyarlathotep and the influence it had on my node-based approach to scenario design may be well-known to readers of the Alexandrian, and Eternal Lies, while having very little directly in common with that campaign in terms of setting or plot, manages to capture perfectly almost everything that I love about its structure while, in my opinion, improving the actual content within that structure. I’ll also be talking more about Eternal Lies at some point in the near future, but the key element here is that it’s prompted me to run an entire Trail of Cthulhu campaign and that means I need a cheat sheet.

Which means that you get a cheat sheet, too.


I keep a copy of the system cheat sheet behind my GM screen for quick reference and also provide copies for all of the players. Of course, I also keep at least one copy of the rulebook available, too. But my goal with the cheat sheets is to summarize all of the rules for the game. This consolidation of information eliminates book look-ups: Finding something in a half dozen or so pages is a much faster process than paging through hundreds of pages in the rulebook.

The organization of information onto each page of the cheat sheet should, hopefully, be fairly intuitive. The actual sequencing of pages is mostly arbitrary.

Page 1: The core mechanics coupled to a list of the investigative and general abilities. Being able to rapidly identify pertinent investigative abilities that might be able to pull information out of a scene is pretty much the heart and soul of the GUMSHOE system, so I put these lists front-and-center for easy reference during play.

Pages 2-3: I’m not 100% satisfied with the sequencing of information on these pages. (For example, the stuff on “Explosives” should conceptually come under “Combat Options” instead of proceeding it.) But I made some compromises to make everything fit onto two pages instead of three, and in actual play this doesn’t seem to have a significant impact on ease of reference.

Pages 4-5: Similarly, my original intention was to get all the Stability and Sanity rules on one page, but they just don’t fit. So Sanity spills over onto its own page, but fortunately the remaining space is filled up nicely with the rules for Tomes and Magic.

Page 6-7: I knew the “Explosives” table was going to be part of the cheat sheet as soon as I read it in the rulebook. (Explosives may not come up frequently, but that table is too finicky for me not to want it at my fingertips whenever it comes up in play.) I wanted the references for “Credit Rating” handy because it felt important to keep that contextualized. The page on “Firearms” got added later based on the fact that I kept reaching for it during actual play.


These cheat sheets can also be used in conjunction with a modular, landscape-oriented GM screen (like the ones you can buy here or here).

Personally, I use a four-panel screen and use reverse-duplex printing in order to create sheets that I can tape together and “flip up” to reveal additional information behind them. My Trail of Cthulhu screen currently looks like this:

  • Page 1: Basic Mechanics (Credit Rating/Explosives printed on the opposite side, Firearms behind it).
  • Page 2: Basic Combat (with Physical Injury/Recovery/Other Danggers behind it).
  • Page 3: Stability
  • Page 4: Sanity/Tomes/Magic

I hope you find them useful!

Trail of Cthulhu - Kenneth Hite

Well, in this case, mostly untested. Here’s a mechanic I improvised while running Trail of Cthulhu last night:

Mitigation Test:When making a mitigation test, instead of setting a difficulty number the Keeper sets a “worst case quantity”. The Investigator then resolves the test normally (spending points, adding them to their roll, and so forth), but the result of the test is subtracted from the worst case quantity to determine the actual outcome. (In some situations, you might choose to use multiples of the test of the result.)

Example: One of the investigators has been bitten by a Mythos creature and the creature’s poison is turning their flesh to stone. The team’s doctor decides the only way to save their life is to cut away the “infection”. The Keeper calls for a mitigation test using Medicine to determine how much damage the doctor deals to the victim/patient and sets the “worst case quantity” to 12 points of damage. The doctor’s player spends two points, rolls a 4, and manages to perform the procedure while only inflicting 6 points of Health damage (12 – 4 – 2 = 6).

Example: An orphanage is beginning to collapse. An Investigator is trying to rescue as many kids as possible before the building comes down completely. The Keeper calls for an Athletics mitigation test to determine how many kids survive and sets the “worst case quantity” to 6 dead kids. The player asks if he can spend Architecture points to assist (by judging which sections of the building are in most jeopardy) and the Keeper agrees. He spends 3 points and rolls a 2… He’s just not able to find Timmy before it’s too late.

Example: The player is trying to carve a forged copy of a stone tablet, but is under something of a time crunch to get it done. The Keeper sets a “worst case quantity” of 48 hours and calls for a Craft test. The Investigator gets a result of 6, which the Keeper multiplies by 5: It’ll take 48 – 30 = 18 hours to complete the duplicate tablet.

Thanks to Colleen Riley, Phil Henry, Tess Keen, and Sarah Holmberg for being my guinea pigs.

Trail of Cthulhu - Kenneth D. HiteA fellow named Caleb asked me in an e-mail recently why I’m not a fan of the way GUMSHOE handles clues. In writing a reply to him, I think I’ve found a better way of expressing my personal distaste for GUMSHOE’s approach than I have in the past.

Start by considering a scenario with locations A, B, and C.

First, let’s assume that each of these locations contains a clue which points to the next location. GUMSHOE says, “Oh no! What if they don’t find a clue? Then the adventure can’t continue!” And in order to solve this problem, GUMSHOE says, “It’s OK. We’ll just remove the resolution mechanic and we’ll simply assume that the PCs succeed.”

Investigative scenarios have been done wrong since the early days of roleplaying games. As a consequence, they’re hard to run and prone to grind to a halt. (…) You have to search for the clue that takes you to the next scene. If you roll well, you get the clue. If not, you don’t — and the story grinds to a halt. (…) GUMSHOE, therefore, makes the finding of clues all but automatic, as long as you get to the right place in the story and have the right ability. (Esoterrorists, pg. 26-27)

In other words, we’ll remove the chokepoint of failure by simply removing the possibility of failure.

So what’s the problem?

Well, now let’s assume that each of these locations contains a monster which you have to fight before you move to the next location.

Presented with this problem, we would expect GUMSHOE to say something like, “Oh no! What if they don’t defeat the monster? Then the adventure can’t continue!”

And in order to solve this problem, GUMSHOE would then say, “Well, that’s OK. We’ll just remove the combat system and we’ll simply assume that the PCs always defeat their foes.”

To be fair, GUMSHOE is right: If you make it so that the PCs automatically win, then they will never lose. It’s tautological and everything. And is there anything wrong with that?

Not necessarily: If the game wasn’t actually about fighting people, there might be little harm in skipping past the fights. But if the game was about combat, then you might have a problem.

And, in my opinion, the actual act of investigation is, in fact, a relatively major component of what a mystery story is about. GUMSHOE says it isn’t because you never see a fictional detective miss a clue. (But if they did miss a clue completely and entirely, how would the reader or viewer ever know? And, in point of fact, there are many mystery stories in which the detective does miss a clue and later goes back to find it or realizes that they missed it only after the crime has already been solved.)

In addition to this, as I’ve discussed in the past, GUMSHOE’s “solution” doesn’t actually solve the problem it claims to be solving: Failing to find a clue is only ONE of the ways in which the clue can fail. Since the problem hasn’t actually been solved, you still need to implement the ACTUAL solution to the problem (which is to not design your adventure around chokepoints in the first place). And once you’ve implemented the actual solution, you’ll discover that characters failing to find any particular clue is no longer any sort of problem… which means that the GUMSHOE “solution” isn’t required at all.

Untested: D20 Piggybacking

November 3rd, 2010

One of my long-standing concerns with the D20 system was the skewed probabilities of opposed group checks. For example, consider the example of a PC making a Move Silently check opposed by an NPC’s Listen check where both characters have the same skill modifier. In this scenario, a single PC attempting to sneak past a single NPC has a 50% chance of succeeding.

Compare this to a situation in which 5 PCs are attempting to sneak past 5 NPCs (with, again, all of the characters involved having the same skill modifiers). This effectively becomes a check in which the 5 PCs are rolling 5d20 and keeping the lowest result, while the NPCs trying to detect them are rolling 5d20 and keeping the highest result.

The average roll of 5d20-keep-lowest is 3. The average of 5d20-keep-highest is 17. That 14 point differential means that it’s virtually impossible for a party of characters to sneak past a group of evenly matched opponents. (And even sneaking past a single watchman is difficult as the average party roll of 3 is opposed by an average roll of 10.)

Of course, the odds are actually worse than this: A successful stealth attempt will also usually require a Hide vs. Spot check, so you need to succeed at not one but two checks at these outrageous odds. And this assumes that the PCs all keep their stealth skills maxed out (which in practice they won’t, particularly since it’s so pointless to do so).

The argument can certainly be made that this is realistic in some sense: A large group should have a tougher time sneaking past a sentry than one guy and more eyes means more people who can spot you. But I would argue that the probability skew is large enough that it creates results which are both unrealistic and undesirable.

In practice, the effects of the skew are obvious: Group stealth attempts quickly drop out of the game. When stealth is called for, it takes the form of a sole scout pushing out ahead of the rest of the group. And when the scout becomes too fragile to survive when the check finally fails, stealth stops being a part of the game altogether.

Since I’d prefer stealth to be a potentially viable tactic, a solution is called for.


DISTANCE / DISTRACTION PENALTIES: A guideline that can really help the stealther is the -1 penalty per 10 feet that is supposed to be applied on Listen and Spot checks. Keep about a hundred feet away from the guy trying to spot you and you can quickly cancel out the probability skew of the dice.

Unfortunately, these modifiers become kind of wonky, particularly when it comes to Spot checks. On the open plains, for example, the “maximum distance at which a Spot check for detecting the nearby presence of others can succeed is 6d6 x 40 feet”. The minimum distance of 240 feet, therefore, is supposed to impose a -24 penalty and the maximum distance of 1,440 feet impose a -144 penalty.

I’ve tried a few different ways of fixing these modifiers, but am currently just using an ad hoc sense of what the range of the check is.

TARGET NUMBERS: Instead of making these opposed checks, set a target number for the PC’s skill check of 10 + the NPC’s skill modifier. (This essentially halves the probabilty skew.)

GROUP CHECKS: Make only one check for each group. But what skill modifier to use? Using the average value is cutesy, but impractical at the game table. Using the lowest value still effectively takes group stealth off the table. Using the highest modifier means that everyone except the rogue ignores the stealth skills entirely and also creates issues with determining surprise.

And how big can a group be? One guy with a decent Hide check shouldn’t be able to sneak an army of ten thousand soldiers under the nose of a watchtower, but where do you draw the line?

Maybe you could limit the number of people covered by a check to equal the skill leader’s skill ranks? Or impose a -2 penalty per person in the group?

COMBINE STEALTH / PERCEPTION SKILLS: I’ve been folding Hide/Move Silently into a Stealth skill and Listen/Spot into a single Perception skill intermittently since 2002, so I wasn’t particularly surprised when both Pathfinder and 4th Edition went in the same direction. It cuts down on dice rolls and eliminates the undesireable “need to succeed twice” feature of stealth checks.

This does create some interesting oddities around trying to resolve invisibility, and while I haven’t found the perfectly elegant solution yet, this slight corner case is (in my experience) preferable to the constantly degrading effects of splitting the skills.

Using some combination of these solutions tends to mitigate the problem, but I’ve generally been unsatisfied with the hodgepodge fashion of it all. So taking my unified Stealth and Perception skills in hand, I’ve been looking for a more elegant solution.


Esoterrorists - GUMSHOEI found the roots of what I think may prove a usable mechanic in the GUMSHOE system:

When a group of characters act in concert to perform a task together, they designate one to take the lead. That character makes a simple test, spending any number of his own pool points toward the task, as usual. All other characters pay 1 point from their relevant pools in order to gain the benefits of the leader’s action. These points are not added to the leader’s die result. For every character who is unable to pay this piggybacking cost, either because he lacks pool points or does not have the ability at all, the Difficulty Number of the attempt increases by 2.

Obviously the point-spending mechanics which underlie the GUMSHOE system can’t be translated directly into the D20 system, but the basic structure of a lead character making a check onto which others could “piggyback” was inspiring.


When the whole group needs to perform a single task collectively (like sneaking past a guard or using group-climbing techniques to scale a cliff) they can make a piggybacking skill check.

(1) One character takes the lead on the check. This character makes the skill check using their normal skill modifier, just like any other skill check.

(2) Other characters can “piggyback” on the lead character’s check by succeeding on a skill check. The Piggyback DC of the check is equal to half its normal DC. (So if the leader is making a DC 30 check, the other characters must make a DC 15 check to piggyback on the check result.)

(3) The lead character can reduce the Piggyback DC by 1 for every -2 penalty they accept on their check. (They must make this decision before making the check.)

(4) The decision to piggyback on the check must be made before the leader’s check is made.

OPPOSED PIGGYBACKING CHECKS: The DC of the check is set by the lead character’s check. Just like any other piggybacking check, only characters who succeed on the piggybacking check benefit.

(To simplify the resolution, you can start by rolling only the lead characters’ checks. After you’ve determined which lead character succeeded, you can call for the necessary piggybacking checks. Anyone piggybacking on the failed check, of course, will fail no matter what their piggybacking check would have been.)



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