House Rules

Optional Rules in Use


Spending Luck

After the player has made a skill roll (using a skill or characteristic), Luck points may be spent to alter the result. The player can use Luck points to alter a roll on a 1-for-1 basis. The points spent are deducted from the investigator’s Luck score, which will reduce the chance of passing a future Luck roll.

Luck points may not be spent on Luck rolls, damage rolls, Sanity rolls, or rolls to determine the amount of Sanity points lost. A player may spend any amount of Luck points (up to their current Luck value) on a roll. A player may only spend Luck to alter one of their own dice rolls.

When a skill roll is failed, the player has the option to push the roll OR spend luck; Luck points may not be spent to alter the result of a pushed roll.

Criticals, fumbles, and firearm malfunctions always apply, and cannot be bought off with Luck points. Also, no skill improvement check is earned if Luck points were used to alter the dice roll. In play, an investigator’s Luck will fall through spends and rise through recovery (see below).

Recovering Luck Points

After each session in-game day of meaningful activity or each down-time scene, each player may make an improvement check for their Luck. This is rolled in the same way as for skill improvement. The player rolls 1D100 and if the roll is above their present Luck score they add 1D10 points to their Luck score. If the roll is equal to or less than the investigator’s present Luck score, no points are recovered. Meaningful activity is defined as a day’s worth of adventuring or investigating. Down-time scenes are defined as the entire stretch of days from one day of meaningful activity to another, such as resting and travel.

An investigator’s Luck score will vary throughout play, but may not exceed 99. The Luck starting value is not used again in the game. There are no resets and the starting value can be exceeded in play.

Spending Luck to Remain Conscious

If you are using the optional rule for spending Luck points to alter rolls, Luck may be spent to remain conscious for a few extra rounds. Remaining conscious until the end of the current round costs 1 point of Luck. The cost doubles on successive rounds—2, 4, 8, and so on—and should be spent at the start of each round. This is is a mixed blessing, as an active character may present a more attractive target for further damage.

Shooting at a Target Through Cover

In some instances of partial concealment, the attacker may choose to shoot through the cover in an attempt to hit the target. In this case add one penalty die (as for partial concealment) and apply an armor rating for the type of cover, for example a low brick wall could provide an armor rating of 10, whereas a thin wooden fence might only give 1 point of protection (see Armor page 108).

Point-Blank Revisited

The point-blank bonus die does not apply to long or cumbersome weapons such as rifles, full-length shotguns, and bows, as these are less easily brought to bear on a moving target at close range. Short-barreled shotguns (of the kind designed for home defense) or sawn-off shotguns do gain the point-blank bonus die.


A prone character is assumed to be lying flat on the ground.

  • Kicking someone when they are down is easier; fighting attacks made against a prone character gain one bonus die.
  • A character that is prone may stand up when they successfully dodge or fight back against an opponent. Alternatively, when it comes to their turn in the round, they may stand up and then take their action.
  • Lying down provides a stable position from which to shoot; a prone character gets one bonus die when making a Firearms roll.
  • By lying flat at on the floor you present a smaller target; those targeting a prone character with a firearm get one penalty die (ignore this if at point blank-range).


Table III: Other Forms of Damage (see page 124) covers mild, strong and lethal poisons in a simplified manner, and is likely to be all you need in the game. If you wish to focus on a specific type of poison and its effects, you may find this more detailed guide useful.

All poisons are divided into four bands: very mild, mild, strong and lethal. The bands indicate the deadliness of the poison, and assume a single dose (application, draft , bite or sting—depending on how the poison is administered). If multiple doses are received, the victim adds a penalty die to their CON roll.

The speed at which the poison acts is determined by the administration method and Keeper discretion. Fast-acting poisons begin to work within a single round (death from cyanide poisoning could be expected within a minute, for example). Slower poisons may take hours or even days to register their effects.

Individual poisons cause a range of different symptoms, including stomach pains, vomiting, diarrhea, chills, sweats, cramps, jaundice, altered heart rate, impaired vision, convulsions, unconsciousness and paralysis. It is up to the Keeper whether the symptoms permit the victim to act or not, or to act with a penalty die or an increased level of diffculty.

Alongside the various symptoms, poisons also cause physical damage.

  • Very Mild poisons: no damage, only temporary unconsciousness.
  • Mild poisons: 1D10.
  • Strong poisons: 2D10.
  • Lethal poisons: 4D10.

Those who succeed in rolling equal to or below a fifth of their CON suffer a lesser effect. Damage should be halved and symptoms reduced as decided by the Keeper. In certain circumstances, Keepers may allow a poison’s effects to be shaken off if the CON roll is a critical success. A character might push the CON roll by attempting to purge the poison, through vomiting, amputation, or bloodletting, for example. Whether these things would work in real-life is questionable—what matters is the drama.

Mythos Hardened

When an investigator’s Cthulhu Mythos skill rises above the value of his or her Sanity score a turning point has been reached. That investigator’s understanding of the universe undergoes a paradigm shift that results in a permanent change to their personality and comprehension of their place in the cosmos. How this is portrayed is left open to the player. The player may decide that his or her investigator’s mind is inured to the horror, no longer cares, or has a more profound understanding that is no longer shaken by the truth. From that point onward, all Sanity point loss is halved. Once this change has taken place it is permanent and will not revert if the investigator’s Sanity should rise above their Cthulhu Mythos knowledge.

House Rules

Fatigue and Exhaustion

A character may be subject to a CON and/or POW roll to determine how their body and mind deal with the stresses accumulated over time, particularly with a lack of rest to recover. Failure to cope will result in Fatigue, which adds a penalty die to certain stressful tasks till adequate rest is achieved. Further failure worsens the condition to Exhaustion, which adds 2 penalty dice to certain stressful tasks till adequate rest is achieved.

Getting less than 4 hours of restful sleep in conjunction with stressful events can trigger a coping test. Getting over 4 hours of rest – but less than 8 – when already affected allows another check, which if passed clears the condition. Getting over 8 hours of rest automatically clears the condition.

As with most other tests, you can add beneficial factors giving you a Bonus die, Spend Luck, or Push the roll. Possible narrative complications resulting from a failed Push could include horrible nightmares calling for a mild (0/1d2) Sanity check, an overnight attack, manifestation of minor (1d3 HP) physical injury, etc.

For clarity, Fatigue does not represent being a little tired. It represents failure to cope with stress and lack of rest, resulting in a severe loss of function. A common anecdote would be “My butt is dragging today.” Exhaustion is an extreme form of this and would be representative of barely being able to think clearly or physically function.

House Rules

Masks of Nyarlathotep Garrion