Arkham Stories (I.e. the Cthulhu-hack I use)

 Those are the rules I use for my Chtulhu-esque investigation games. I like BitD, so it's inspired by that system. 

Rules:

Action roll: 

Action-rolls are the mechanism we use to resolve conflicts in this game. When the Investigators want to do something, and there is an interesting obstacle between them and what they want, they roll a number of d6 equal to the rating of the Action they use to overcome the obstacle. Then we look for the highest number rolled.

If the highest die of the roll shows a 3, the Investigator fails - they should be ready for the worst (in RPG-speak: 'the GM gets to make a move'). Something goes wrong in some way or another, and the GM can introduce a new complication, AND the obstacle isn't overcome. If the highest die shows a 4 or 5, the Investigator gets what they want and they overcome the obstacle, however, they might have to pay a price to do so(in RPG-speak: 'the GM gets to make a move' also). If the highest die shows a 6, they succeed without repercussions. If the dice show more than one 6, they critically succeed and get +1 Effect. The idea is that the GM never rolls any dice but simply moves when the narration demands, when the Investigators ignore an obvious danger, or when an Investigator gets no 6 on an Action-roll.

The Investigators:

• Takes 1d6 per rating of the Action they are using.
• Takes +1d6 or +1 Effect if they get any help at all. Everyone helping is in the line of fire for consequences.
• Takes +1d6 or +1 Effect per significant advantage ( great tools, great plan etc. )
• Push-Yourself: Investigators can choose to push themselves. To do so, after any Action-roll but only once per roll, they can reduce their current Body or Mind (see that section) by 1 and reroll any of the dice.

If the Investigator has 0 dice left after accumulating a dice pool, they roll 2d6 but look at the worse of the two to evaluate the roll.

Aside from the potential dangers involved with acting on the word, another factor is how effective the Action is in overcoming an obstacle. That's where 'Effect' comes in. Every Action has an Effect of 1 and is modified by the schema above and by Perks. Actions that are very unlikely to succeed, either because of narrative disadvantages or because an approach was chosen unwisely, can have -Effect. This means that the Investigators will have to make do with less than what they need to overcome an obstacle fully. Even Actions with an Effect of 0 should have some effect; they are just very limited in scope.

The way to think about Effect and more complicated obstacles is to treat them as extended tests on which Effect accumulates until the obstacle is overcome. Nowadays, extended tests are called 'Clocks', the syntax being that a 6-Clock requires a total Effect of 6 from different Actions to overcome. For instance, if escaping the cultists is a 6-Clock, Actions with a total Effect of 6 must be accrued to escape them. For more complicated obstacles, writing the Clocks down is helpful, though just keeping Clocks in the back of the head for smaller situations is enough.

As a general rule of thumb: Whenever an Investigator gets more Effect than they need, they should get some extra benefit for every point of Effect. That means, if they got +Effect and it's just a regular roll where we don't need Clocks they can ask for extra for these rolls.

Resistance:

Resistance-rolls are a special kind of Action-rolls unilaterally demanded by the GM when an Investigator has to endure mental or physical hardship. Resistance is rolled with either Endure or Grit-Your-Teeth. Aside from that, they work like any Action-roll.

Body & Mind:

Whenever an Investigator suffers mental or physical harm, they roll a number of d6 = to their Mind or Body rating, depending on the nature of the suffering. They reduce the number of dice by the Effect of the threat: one if the suffering is particularly severe, by two if it is life-threatening, and by three if it is caused by the mythos. The dice system for Body or Mind rolls works like the-price-is-right; when suffering harm, an Investigator rolls a number of d6 and attempts to get as close as possible to their rating in Body or Mind, respectively. After the roll, the Investigators then reduce their Body or Mind by a number equal to the difference between their current stat (NOT the number of dice rolled) and the closest number rolled. Whenever an Investigator loses Body or Mind, they are narratively injured, and the GM can ask them to also Resist if they want to do Actions hindered by their untreated injuries. Armour or cover gives extra dice on Body rolls.

If, after a Mind- or Body-roll, the rating is 0, the Investigator is about to break, and if they break, they suffer Trauma. At 0 Mind, any investigator who acts meaningfully has to Resist; Endure if Mind is 0, and Grit-your-Teeth if Body is 0. If they fail to Resist the pain and hardship, they get Trauma. Suffering Trauma hands the GM control of the PC for as long as they deem appropriate, but at most for the investigation: they are antagonistic, knocked out from pain, temporarily insane, or otherwise unhelpful.

Every time an Investigator suffers Trauma, their Bonds suffer with them, and the traumatized Investigator reduces one Bond's rating by 1d6. When a Bond's rating reaches 0, they are gone, and with no Bonds left, Investigators become unplayable.

Investigators can die when the fiction demands (they commit suicide, get thrown out of a plane etc.). Mechanically, this is left to the GM's judgement, but should really only be on the table when Investigators are at 0 Body or Mind.

An example: Alex gets shot by a small gun. They try to dodge but fail. Alex's Body rating is currently 4 because they were already injured. It's a gun, so Alex is told to reduce their pool by 1; 3 dice left. Their dice show: 1,1,6. A bad roll. The closest number to their Body (which was 4) is 6, so they reduce their Body by the difference of 4 and 6, which is 2! Now Alex's Body is 2, and because they got an injury, the GM can ask them to Resist the pain when they do things that are too straining.

Special Rules:

I am using these rules to give a little more mechanical depth to some situations that often come up in these sorts of games.

First Aid: When an Investigator is injured during an investigation and gets attended to for first aid, once per injury, they can restore an amount of Body equal to the Effect of the related Action-roll minus 1. Injuries that don't get attended to might require the Investigators to Resist some pain down the road.

Aiming: When an Investigator is aiming and makes sure they take some time for their next shot, they get +1d or +1 Effect for the next attack.

Cover: While behind cover, if an Investigator wants to do anything pro-active themselves, that risks them getting hit, they take +1d on all potential Body-rolls.

 

Investigator Creation:

Action ratings: 

Importantly, the Action Investigators use are verbs, things the Investigators do (to overcome obstacles), not attributes they have. People can be good at noticing things for all kinds of reasons, but we don't really care about why they are good in this game.                     

The Actions should be self-explanatory.

The Investigators start with two Actions at 0, four Actions at 1, four Actions at 2, and two Actions at 3.

• Notice (awareness, hearing, reflexes, searching)
• Assess(interpretation, estimation, insight, analysis)
• Move (Moving oneself and or objects from place A to place B, including sprinting, climbing etc.)
• Charm (Persuasion; being nice and chummy with people)
• Coerce (Intimidating, commanding, and shouting)
• Deceive (Lying, trickery, disguise, misdirection)
• Procure (Buying things, finding the right stores, places, information and people)
• Fix (Making things work again, machines or biological)
• Fight (Fisticuffs and melee weapons)
• Shoot (Shooting)
• Stealth (Being inconspicuous, evading notice, hiding things)
• Endure (Enduring madness and seeing you shouldn't see)
• Grit-your-teeth (Powering through pain and unpleasantness)

Stats:

All Investigators start with the following statistics, though some of them can be customized further through their Perks.

• Body 6
• Mind 6
• Bonds 3
• Preparation 7

Bonds:

Investigators can create a number of Bonds, i.e., touchstones and anchors to keep them sane and working, equal to their related stat.

    

    When creating a Bond, first assign them a Name and a sentence-long description, telling us who they are. The description provides their expertise and the avenue through which they can help the Investigators. Every Bond starts with a rating of 4 and acts as a buffer before the Investigator becomes unplayable.

Preparation:

Investigators have stuff. However, we don't keep lists. To simulate their planning and the stuff they 'always already had' on them (they can find more things during play, of course), we use the Preparation stat.

    During play, every Investigator can 'create' a number of items they already have on them equal to their Preparation rating. Investigators have to make-up where they got the item from (they can't just generate a shotgun from nowhere; the shotgun might be in their car). The items that require Preparation are up to the GM; however, we use Procure to buy things during play. Spent points of their Preparation were spent do refresh every time the Investigators got time to restock their supplies.

Calculating the cost to have an item prepared goes as follows:

Size:

Small: 1 (handheld)

Large: 4 (larger than that)

Unlikely: +1 - +3 (just something that isn't likely for the Investigator to have, +1 would be something unlikely, like a fishing rod in a city, and +3 is something highly specific, like an invitation to a particular party. If it's too out there, the Investigator can't have it.)

Illegal: +1

Expensive: +1

Fine Quality: +3 (gives +1d or +1 Effect)

One-time use: +2 Effect

Equipment opens up the possibility to do things: you can't shoot a gun if you don't have one. If you want to lockpick a door without a proper lockpick, you might have -Effect. Items of a Fine Quality give a bonus; otherwise, small weapons give +1 Effect, and large Weapons give +2 Effect. Armor, such as a bulletproof vest, counts as large and gives +1d on Body-rolls when it applies.

Qualities:

Investigators get to distribute 13 points:

• (1/3) Outdoors-Kid: For 1 Point, the Investigator can always find North, for 3 points, the Investigator can survive outdoors for an infinite amount of time.
• (1/2/3) Good Reputation: The Investigator gets 3 points of Reputation that can be spent to get +1d on social Actions they do that relate to what people might have heard about them. This pool refreshes every session.
• (1) Linguist: The Investigator can speak an additional language. Can be taken multiple times.
• (2/4) First Aid Expert: Once/twice per session, the Investigator can attempt to temporarily Fix the Body of another Investigator. The target heals an amount of Body = the Effect of the Action.
• (2/4) IT-Expert: The Investigator gets +1 Effect when interfacing with a computer. For 4 points, they also get +1d when doing so.
• (2/4) Silent: The Investigator gets +1 Effect to avoid being heard. For 4 points, they also get +1d.
• (2) Veteran: The Investigator can see mundane atrocities without having to Resist them.
• (2/4/6) Know-it-all: 1/2/3 times per Session, the Investigator can provide a useful bit of information from their field of education (as determined by the player). Whenever people use that information for action, they get +1d (does not stack).
• (2)  Well prepared: The investigator starts with +1 Preparation. Can be taken up to 5 times.
• (2) Criminal: The Investigator has easy access to the criminal underground. When rolling to procure illegal goods, take +1 Effect.
• (2) Contortionist: The Investigator can crawl through small spaces and contort themselves in ways not thought possible.
• (2) Secret Identity: The Investigator gets +1d whenever they try to hide their true identity.
• (2) Academic: The Investigator chooses a field of study and gets +1d to know things in relation to that field.
• (2) Innocent-looking: +1 Effect on rolls to de-escalate situations.
• (2) Iron stomach: The Investigator can eat lots of things that might make other folks sick and gets +1d to Endure poisons and +1d on Body tests vs poison.
• (2) Athletic: The Investigator has +1 Effect on rolls to run or jump and on stamina-related tasks.
• (2) Juryrigger: The Investigator can make a machine that's normally just done with the world, and continue until the end of the scene.
• (2) Hawk-eyes: The Investigator's eyes have a regular Effect on longer distances.
• (2) Engineer: The Investigator has to select a specialty for the Fix Action. When the Investigator Fixes their subject, they get a +1 Effect.
• (2) Book Worm: The Investigator gets +1d to research in a library.
• (2) Animal-lover: The Investigator can practically speak with animals (not really, but almost), and animals don't like to hurt them.
• (2) Lucky: The Investigator gets 1 use per session, expending a use after any roll, they can roll an additional d6. Only once per roll and can be taken multiple times.
• (3/6) Trained: The Investigator gets +1 Effect for combat. For 6 points, they also get +1d.
• (3) Scary: Take +1d to scare or intimidate people.
• (3) Official: The Investigator gets +1d to manoeuvre bureaucracies.
• (3) Hotshot Driver: +1d to drive vehicles.
• (3) Likeable: The Investigator starts with an additional friend.
• (3) People Person: The investigator's friends start with an additional rating point.
• (3) Reflexes: When reaction speed is in question, the Investigator gets to react first.
• (3) Sweetheart: The Investigator takes +1d on all actions against people they had some intimacy with.
• (3) Busy-body: The Investigator has +1 Downtime Action.
• (3) Night-owl: The Investigator can see pretty well in (not totally black) darkness, and you are good with little sleep.
• (3) Sucker for Pain: The Investigator gets +1d to endure pain.
• (3) Occultist: The Investigator gets +1d to study and use dangerous tomes.
• (3) Anchored: Once per session, the Investigator can roll a Mind Test again.
• (3) Feline Grace: The Investigator gets +1d to keep balance.
• (3) Scarred: The Investigator starts with knowledge of the Mythos and can resist with Mind to recall Information about it. Additionally, they have -1 max. Mind but take +1d when casting spells or when resisting the Mythos with Mind.
• (3) Well-Connected: The Investigator gets +1d to procure people.
• (3) Fast Recovery: The Investigator gets +1 Effect when using the Recover Downtime-Action.
• (3) Nimble: The Investigator gets +1d for tasks involving sleight of hand, like magic (the non-spellcasting kind) or pickpocketing.
• (3) Martial Arts: The Investigator takes +1d when they fight without attempting to deal damage (like, when they try to disarm, grapple, knock someone prone etc.)
• (4) Tough-skinned: The Investigator takes +1d on Body rolls. (This doesn't change the stat they need to hit with their roll.)
• (4) Iron-willed: The Investigator takes +1d on Mind rolls. (This doesn't change the stat they need to hit with their roll.)
• (4) Well-Off: The Investigator has +1 on Preparation and +1d to procure things with money.
• (4) Photographic Memory: It does what it says.
• (4) Strong: The Investigator has +1 Effect on Move and Fight Actions that involve muscle power.
• (4) Charismatic: Choose one Action from either Charm, Deceive or Coerce. The Investigator gets +1 Effect whenever they use the Action.
• (4) Talented: The Investigator gets an additional point to distribute on their Actions.
• (4) Wing Man: Help of the Investigator gives +1d as well as +1 Effect (instead of only one).
• (5) Assistant: The Investigator has another PC that helps them. The Assistant has all Actions on 0, except one, which is on 2.
• (6) Medium: The Investigator has a supernatural sense to notice Mythos activity.
• (6) Trained to Kill: The Investigator takes +3 Effect on all Actions that attempt to murder someone.
• (7) Sixth Sense: The Investigator can always tell when someone is lying (i.e. when someone is saying something they know is not true, in order to deceive).

Downtime:

After every investigation, the Investigators can take two Downtime-Actions. Every Downtime-Action can only be taken once per Downtime.

Basically, we fill Clocks during downtime. I provided the following Clocks, but the GM can make up new ones depending on what the investigators want to do in the fiction. Furthermore, at the end of Downtime, reset Body and Mind to 6.

• Improve: If you don't have a Clock for this Downtime-Action, create a related 3-Clock. Otherwise, keep working on the old one. Roll Procure. On a 1-3 increase, the Clock by 1 and reduce the rating of a Bond by 1. On a 4-5, increase the Clock by 1. On a 6, increase the Clock by 2. Once the Clock is full, the rating of an Action increases by 1.
• Make new friends: If you don't have a Clock of this Downtime-Action, create a related 3-Clock. Otherwise, keep working on the old one. Roll Charm. On a 1-3 increase, the Clock by 1 and reduce the rating of a Bond by 1. On a 4-5, increase the Clock by 1. On a 6, increase the Clock by 2. Once the Clock is full, create a new Bond with a rating of 1d3. Reduce the rating of a Bond by 1.
• Study: Roll Assess. On a 1-3 get 1 Background point and reduce the rating of a Bond by 1. On a 4-5, get 1 Background point. On a 6 get 2 Background points
• Responsibilities: Increase the rating of a Bond by 1d3.
• Disappear for a couple of days: Roll a test with a number of dice = the remaining Mind at the end of the last investigation. On a 1-3 create a Mind-buffer of 2 and reduce the rating of a Bond by 1. On a 4-5, create a Mind-buffer of 3 and reduce the rating of a Bond by 1. On a 6 create a Mind-buffer of 3. The Mind-buffer does not get rolled but functions as a kind of shield. It gets used before the Mind gets directly attacked.
• Make some money: Increase Preparation by 1. Reduce the rating of a Bond by 1.
• Research: Roll Notice. On a 1-3 reduce the rating of a Bond by 1. On a 4-5, discover a relevant object, person, or piece of information you are attempting to find. On a 6, increase the Clock by 2. Once the Clock is full, create a new Bond with a rating of 1d3. Reduce the rating of a Bond by 1.
• Acquire an asset: The Investigator gets access to a specific piece of equipment, location, person etc. If the asset is difficult to acquire, open a 2-Clock as with Improve or Make new Friends and start filling it by 1 per time you take this Action. Reduce the rating of a Bond by 1.

Additionally, there might be Clocks already in play from the investigations. Those can stay in play, and the Investigators can influence them by spending Downtime-Actions also. For that, they have to say how they do it and then roll an Action. They change the Clock by their Effect as with other Downtime-Actions.

I suggest not just playing out any downtime abstractly but laying plot-hooks and opportunities for Action-Rolls, if the Investigators have the opportunity to find some stuff out during the fiction: let them.

Magick:

As in other Cthulhu-esque games, there are ways to engage the Mythos as Investigators that do not involve running, hiding, or shooting. Some cultists might have access to Magick, and when finding dangerous tomes, the characters might also get access to not only knowledge but also spells.

In case the Investigators get hold of dark tomes and are able to learn some spells, the best way I found to handle them is idiosyncratically. Every tome should have its own rules, dice rolls, and every spell should work slightly differently from all others. A general scheme, which should be filled out more dutifully by the GM, could look like so:

Reading tomes requires an Action-roll. Most likely, Asses, Endure, and Procure; but others are thinkable depending on the work. Maybe the Investigator has to softly whisper charming words so the book opens up to them? Afterwards, there should be some kind of Mind-roll with a modifier depending on how bad the tome is. Knowledge is dangerous. Having read the tome should always give a narrative benefit: now the Investigator knows something relevant they didn't before. Maybe the weakness of a horror, or maybe a new clue where to go next.

Tomes could include spells. I think learning a spell really depends on the spell and the tome. If it's a quick chant, maybe the Investigator can learn it just while studying the tome, with no further roll needed, but maybe it's a hidden ritual that has to be uncovered with more rolls.

Spells that are uncovered can be used (who would have guessed). Spells should be handled individually, also. There are different axes that can be modified to create an individual spell.

Magick: What does the spell actually do? I think the best spells have effects that are explainable otherwise. Only powerful Magick should be visibly magical.

Action: Does the spell require an Action to cast, or does it just work?

Mind: Whenever an Investigator casts a spell, they must roll with Mind. Casting spells destroys the mind. However, powerful Magick might even remove some dice, max. 3.

Body: In addition, some Magick might require a Body-roll since it drains the life of the caster.

Time: How long does casting the spell take? A few seconds, hours, days? Is it a ritual?

Ingredients: Does the spell require special preparation? Some ingredients are easy to gather, but for some, the Investigators might need to spend time, money, and effort to gather.

Memorization: Can the spell be learned by heart, or does the caster require notes of the incantation?

I think the best spells are just designed by the GM, for the book it can be found in, and for a specific investigation or campaign.