Sanity System for Horror RPGs
The sanity system simulates the psychological toll of encountering cosmic horror and supernatural terror. These rules are primarily based on Call of Cthulhu but can be adapted to any horror RPG system.
🧠 Sanity Basics
Maximum Sanity
Call of Cthulhu: Maximum SAN = 99 minus Cthulhu Mythos skill
Starting SAN: Equal to POW (Power) statistic
Range: 0 (completely insane) to 99 (untouched by horror)
Current Sanity
Current SAN represents your investigator's present mental state. It decreases when encountering horrific events and increases through successful treatment or the passage of time.
High Sanity
75-99 SAN
Mentally stable and rational
Fragile Mind
25-74 SAN
Vulnerable to horror
Breaking Point
0-24 SAN
On the edge of madness
📉 Sanity Loss Table
When encountering horrific events, roll the indicated dice and lose that many Sanity points:
| Event Type | SAN Loss (Success) | SAN Loss (Failure) |
|---|---|---|
| Mundane Horror | ||
| Finding a mutilated corpse | 0 | 1d3 |
| Witnessing a murder | 0 | 1d4 |
| Accidentally killing someone | 1d3 | 1d6 |
| Committing murder | 1d4+1 | 1d6+2 |
| Torture | 1d3 | 1d6 |
| Supernatural Events | ||
| Seeing a ghost | 1 | 1d6 |
| Witnessing black magic | 1d2 | 1d6 |
| Seeing a zombie | 1d6 | 1d10 |
| Witnessing dark ritual | 1d4 | 1d8 |
| Possession witnessed | 1d3 | 1d8 |
| Minor Mythos Creatures | ||
| Ghoul | 0 | 1d6 |
| Deep One | 1 | 1d6 |
| Mi-Go | 1d2 | 1d6 |
| Shoggoth | 1d6 | 1d20 |
| Major Mythos Entities | ||
| Star Spawn of Cthulhu | 1d6 | 1d20 |
| Byakhee | 1d3 | 1d10 |
| Dark Young | 1d8 | 1d20 |
| Great Old One (Cthulhu, Hastur, etc.) | 1d10 | 1d100 |
| Outer God (Azathoth, Yog-Sothoth, etc.) | 1d10 | 1d100 |
😱 Temporary & Indefinite Insanity
Temporary Insanity
Triggered by: Losing 5+ SAN from a single event
Duration: 1d10 rounds or hours (Keeper's choice)
Effects:
- Character becomes unplayable temporarily
- Roll on Temporary Insanity table
- Screaming, fainting, fleeing, catatonia
- May attack friends in confusion
- Keeper controls character during episode
Indefinite Insanity
Triggered by: SAN drops to 0 or losing 20% of current SAN at once
Duration: Until treated (therapy, time, etc.)
Effects:
- Develop phobia or mania
- Character may become NPC
- Requires professional treatment
- 1d6 months institutionalization
- May never fully recover
😨 Phobias (d100)
When gaining indefinite insanity, roll on this table for specific phobia:
| d100 | Phobia |
|---|---|
| 01-05 | Acrophobia (heights) |
| 06-10 | Agoraphobia (open spaces) |
| 11-15 | Arachnophobia (spiders) |
| 16-20 | Claustrophobia (confined spaces) |
| 21-25 | Hemophobia (blood) |
| 26-30 | Hydrophobia (water) |
| 31-35 | Necrophobia (death/corpses) |
| 36-40 | Nyctophobia (darkness) |
| 41-45 | Ophidiophobia (snakes) |
| 46-50 | Pyrophobia (fire) |
| d100 | Phobia |
|---|---|
| 51-55 | Taphophobia (being buried alive) |
| 56-60 | Thanatophobia (death itself) |
| 61-65 | Xenophobia (strangers/foreigners) |
| 66-70 | Zoophobia (animals) |
| 71-75 | Monophobia (being alone) |
| 76-80 | Trypanophobia (needles/injections) |
| 81-85 | Mysophobia (germs/contamination) |
| 86-90 | Ornithophobia (birds) |
| 91-95 | Phasmophobia (ghosts) |
| 96-00 | Keeper's choice (specific to event) |
🌀 Manias (d100)
Alternatively, roll for a compulsive mania:
| d100 | Mania |
|---|---|
| 01-10 | Kleptomania (compulsive stealing) |
| 11-20 | Pyromania (compulsive fire-setting) |
| 21-30 | Mythomania (compulsive lying) |
| 31-40 | Megalomania (delusions of grandeur) |
| 41-50 | Paranoia (everyone is out to get you) |
| d100 | Mania |
|---|---|
| 51-60 | Dipsomania (compulsive drinking) |
| 61-70 | Trichotillomania (hair pulling) |
| 71-80 | Erotomania (delusions of love) |
| 81-90 | Monomania (single obsessive idea) |
| 91-00 | Keeper's choice (related to trauma) |
💚 Sanity Recovery
Natural Recovery
- Time: Regain 1d3 SAN per month of rest and normalcy
- Defeating Evil: Regain SAN equal to Mythos creature's SAN loss (failure value)
- Resolving Mystery: Keeper may award 1d6 or 1d10 SAN for solving case
- Limits: Cannot exceed starting or maximum SAN
Professional Treatment
Psychoanalysis
- Requires trained psychiatrist
- 1d3 SAN restored per successful day
- One roll per day maximum
- Expensive ($50-100 per session in 1920s)
Institutionalization
- For indefinite insanity
- 1d6 months minimum stay
- May regain enough SAN to function
- Phobias/manias may remain
💡 Using Sanity Rules in Your Game
For Keepers/GMs
- Call for SAN rolls at dramatic moments
- Don't overuse - preserve impact
- Match loss to horror severity
- Use temporary insanity for drama
- Make indefinite insanity meaningful
- Allow recovery opportunities
Adapting to Other Systems
- Scale SAN to your system (1-100, 1-20, etc.)
- Adjust loss amounts proportionally
- Tie to Wisdom, Will, or similar stat
- Create system-specific phobias/manias
- Balance with your game's tone
- Focus on narrative over mechanics