Call of Cthulhu 7e Temporary Insanity Guide

Introduction

Temporary insanity is the moment Call of Cthulhu turns a bad Sanity roll into a scene with consequences. It is not a label for a character, a diagnosis, or permission to make a player the table's spectacle. It is a tightly defined horror-game procedure: a large single loss of Sanity may produce a short loss of control, followed by a limited period in which another shock can set that response off again.

That structure matters. Treating every failed SAN roll as temporary insanity makes the game exhausting and blunts the rule. Treating temporary insanity as an excuse for random violence makes it shallow and can make the table unsafe. Used well, it creates an immediate, character-specific problem that the group can respond to together, then leaves a short aftershock that makes the next discovery more dangerous.

This guide covers the core procedure and practical table decisions. Start with the broader Sanity System guide and Sanity rules guide if the moving parts of SAN loss are still new.

Hot Take

Rolling on the bout table while the whole table watches is the worst way to run this rule. It takes the character away for ten minutes and usually produces a generic freak-out. A good bout gives the group a sharp, human problem for a few beats, then hands the character back with a new complication that everyone remembers. A character who runs because the room suddenly resembles the childhood house where a sibling vanished is more useful than a character who is simply declared "unpredictable."

Temporary Insanity at a Glance

The core sequence is short:

1. An investigator loses 5 or more SAN from one source.
2. The Keeper calls for an INT roll.
3. A failed INT roll means the investigator represses the experience. They do not become temporarily insane from that event.
4. A successful INT roll means they understand enough of the event's significance to become temporarily insane.
5. Temporary insanity begins immediately and lasts 1D10 hours (or until a good night's sleep in a safe place).
6. The first phase is a bout: a brief loss of self-control, usually resolved in a few rounds or summarized if the character is alone.
7. The second phase is underlying insanity: the player regains control, but any further SAN loss during the remaining duration triggers another bout.

Keep that last distinction visible. The bout is the scene. The 1D10-hour duration is the vulnerability that follows it. A player who has returned to ordinary conversation is not automatically fine in mechanical terms.

The Single-Source Trigger

The threshold is five or more SAN lost from one source, rather than five accumulated across a session, a combat, or a grim afternoon. A single revealing scene, creature, spell, body, or other defined horror can qualify; several separate one-point losses do not combine for this rule.

That makes the value written after a failed SAN check important. Record what caused the loss and how much came from that cause. A Keeper who only tracks the running total has to reconstruct the actual trigger later.

For example, Elsie fails a check after seeing something emerge from a flooded dock and loses 1D6 SAN. She rolls a 5. That single source clears the threshold, so the Keeper calls for INT. If she had instead lost 2 SAN from a corpse, 1 from a strange sound, and 2 from a threatening cultist, that is not one five-point loss and does not create temporary insanity under this procedure.

This is separate from the larger daily-loss rule that can lead to indefinite insanity. Do not quietly combine the two because both happen to use Sanity. One measures an acute realization; the other measures cumulative strain.

Why the INT Roll Seems Backward

At first glance, asking for INT after a huge SAN loss can feel counterintuitive. In this procedure, success is not a reward. A successful INT roll means the investigator grasps enough of what happened for the knowledge to land. That recognition produces temporary insanity.

Failure means repression. The investigator cannot or will not connect the event to its full implication, so the temporary-insanity procedure does not begin. The loss of SAN still happened. The event can still matter in the story. It simply did not become this particular mechanical state.

That is useful roleplaying information, not an invitation to tell the player what their character really thinks. A player might describe repression as blank memory, frantic rationalization, emotional numbness, or an insistence that the dock was only a fever dream. Let the player choose language that fits the investigator and the table's content boundaries.

In Elsie's example, a successful INT roll might mean she realizes the shape was not a drowning victim. She starts screaming that the water is listening. A failed roll might mean she remembers only cold rain and the need to get away, with the rest of the scene blurred out.

Phase 1: A Bout

When temporary insanity begins, it begins now. The first phase is a bout in which the investigator loses self-control. The Keeper directs the immediate outcome, but the goal is a dramatic interruption with a clear endpoint, not a punitive cutscene.

When other investigators are present and can intervene, the bout is normally played in real time for 1D10 combat rounds. The Keeper can give the player a narrow direction or take brief control, then return meaningful choices as soon as another investigator can engage. A companion who talks Elsie down, blocks the exit, or follows her through the rain gives the player a way back into the scene.

When the investigator is alone, far from the group, or the entire group is affected, summarize the bout instead. The Keeper can establish what the character did and where they end up, typically accounting for 1D10 hours of elapsed time, or whatever the Keeper judges appropriate. Do not use summary to confiscate clues, equipment, or dignity without a conversation. It is stronger when the summary creates a playable lead: Alaric comes back to himself on a tram with muddy shoes, an unopened envelope in his pocket, and a memory of being certain the university archives were unsafe.

During a bout, the investigator is immune to further Sanity loss. That prevents a stack of horror stimuli from turning one moment of lost control into a recursive rules problem. Once the bout ends, ordinary SAN consequences matter again, including the underlying-insanity trigger below.

Choose a Direction, Not a Stereotype

The Keeper Rulebook provides tables for bout outcomes, and you do not need to roll them blindly to run a good scene. Pick a direction connected to the event, the investigator's established history, and the group's consent, then give it an objective the rest of the table can see and respond to. The Bouts of Madness Guide sets out the six directions worth reaching for, alongside the material to leave alone without explicit agreement.

Scale matters more than volume here. A quiet fixation on preserving a damaged photograph may be more unsettling, and more playable, than any loud outburst.

Phase 2: Underlying Insanity

After the bout, the player resumes control. The investigator can converse, investigate, and make ordinary decisions. Temporary insanity is not a command to keep performing distress at every moment for the next several hours.

The mechanical consequence is fragility. For the rest of the 1D10-hour duration, any additional Sanity loss, even one point, causes another bout of madness. The new bout is a fresh immediate scene. The rules do not say whether it restarts the 1D10-hour clock, so the Keeper decides and should say which before play continues. Track the end time at the table so no one has to guess whether the window is still active.

This is why a Keeper should not casually add Sanity checks during the window. The game is telling you that a small new shock can have an outsized response. Use that fact to make later horror meaningful, not to spring an arbitrary trap. If the group must choose between opening the cellar tonight or returning at dawn, the temporary-insanity clock gives that choice weight.

Elsie rolls a 5 for duration. Her first bout at the docks ends after several combat rounds, and she becomes playable again. Three hours later, the group opens a shed and she loses 1 SAN from a new event. Because she is still within the five-hour period, that one point triggers another bout. The 1 SAN is still only 1 SAN; the bout comes from the active temporary-insanity state, not from reaching the five-point single-source threshold again.

Mythos-Related Temporary Insanity

If temporary insanity is caused by a Mythos-related event, it can also improve the investigator's Cthulhu Mythos skill. The first Mythos-related temporary or indefinite insanity gives 5 percentage points of Cthulhu Mythos. Each later Mythos-related temporary or indefinite insanity gives 1 point. Non-Mythos insanity does not award the skill.

That benefit is not a prize for pursuing distress. It represents knowledge that has become impossible to fully dismiss, and it comes with the long-term ceiling on Sanity explained in the maximum Sanity and Cthulhu Mythos guide. Record the gain when it happens and state why the event was Mythos-related, so the table does not have to litigate it months later.

Make the Consequence Fit the Character

Temporary insanity works best when the Keeper and player revise or add a small piece of backstory together. This is not a demand that a player disclose anything personal. Fictional anchors are enough: an old colleague, a childhood superstition, a case the investigator never solved, a favorite safe routine, or a promise they made before becoming an investigator.

Before play, each player can offer two or three optional hooks: a place they avoid, a responsibility they protect, and an ordinary comfort that horror could distort. The Keeper has a menu, while the player retains the right to say no. During play, one question can do the work: "What does this sight make your investigator afraid they have failed to protect?"

For Alaric, the answer may be the university library where his mentor disappeared. A temporary-insanity bout after reading a forbidden passage might lead him to lock the relevant book away and leave a warning with a librarian. The group can find him, challenge his decision, or use the warning as evidence. The outcome is connected to the character, and it leaves the next scene richer than a random detour.

Player Guidance

Tell the Keeper what kinds of loss-of-control scenes are interesting for you before the campaign begins. A useful preference is concrete: "I am happy with flight, fixation, and lost time; do not use harm to children or self-harm." You can update that preference as the campaign changes.

When a bout occurs, look for a playable impulse instead of trying to perform a medical condition. You might insist on leaving, protect an irrelevant object, demand to verify one fact, or become certain that a trusted location is unsafe. Give the other investigators something they can respond to. Once they intervene, take back the character and decide whether they feel embarrassed, defensive, grateful, or unwilling to explain.

During the underlying period, play the pressure without monopolizing the table. Your investigator can still make plans and solve clues. Let the possibility of another bout inform their choices: perhaps they delegate the next inspection, stay close to a trusted companion, or push ahead because the case cannot wait. The interesting question is not "how erratic can I be?" It is "what does this experience cost this person right now?"

Keeper Guidance

State the procedure plainly when it triggers: "That was five SAN from one source. Please roll INT. On a success, we will establish a brief bout and then track 1D10 hours of underlying instability." Clear framing protects trust because the player knows what rule is being applied and what their choices will look like afterward.

Before choosing or rolling an outcome, take ten seconds to ask for boundaries and a character hook. You can say, "Would flight, fixation, or a time skip be enjoyable here? Is there something from your investigator's past this could touch?" If the player is not comfortable improvising, offer two options and let them pick. The game does not require an emotionally intense monologue to make the rule work.

Keep a bout bounded. Give it an objective, a visible way for companions to intervene, and an end state that returns the player to the group. Avoid using temporary insanity to reveal secret player-character information, force PvP, erase resources, or impose a campaign-changing decision without consent. The horror should create pressure, not take ownership of someone else's character away for the evening.

Finally, track the duration in the open. Note when the 1D10 hours expire, remind the player when a later SAN loss could trigger a bout, and call for a brief pause or check-in if the scene becomes more intense than expected. Safety tools are table practices, not an extra core rule, but they make it easier to use the core rule well.

Temporary Insanity Checklist

When the loss happens:

• Confirm that one source caused a loss of 5 or more SAN.
• Call for INT and explain that success means recognition, not protection.
• On an INT failure, record the SAN loss and let the investigator repress the event.
• On an INT success, roll 1D10 hours and establish the immediate bout.

During the bout:

• Use 1D10 combat rounds when other investigators can intervene; summarize when separation makes that impractical.
• Choose a character-linked direction with the player where possible.
• Remember that further SAN loss does not apply during the bout.
• End with a clear handoff back to player control.

After the bout:

• Record the expiry time for underlying insanity.
• Trigger a new bout if any later SAN loss occurs before that time.
• Apply Cthulhu Mythos advancement only for Mythos-related temporary insanity.
• Check in after the session and carry forward any new fictional hook only if the player wants it.

Temporary insanity should leave a mark on the investigation, not derail it. The group has seen what the horror can do to one of its own. Now it has a reason to be careful, a new way to understand that investigator, and a sharper decision the next time the dark asks them to look closer.