Chaosium’s Basic Roleplaying Rules

Homebrews, Rules

These edited rules are mostly based on Chaosium’s Basic Roleplaying, 4th edition, with additions from various Call of Cthulhu editions and bits from other games (like D&D5e’s simple Advantage/Disadvantage instead of CoC7e’s version of the same rule).

Also see: Basic Roleplayer System Reference Document

CHARACTER STATS

Basic Characteristics: Characters have the following abilities:

  • Charisma: Force of personality, charm, persuasion, leadership.
  • Constitution: Health, vigor, toughness, resistance to disease.
  • Dexterity: Agility, coordination, precision, quickness, reflexes.
  • Education: Understanding of technology, arts, sciences, humanities.
  • Intelligence: Mental acuity, logic, memory, reasoning, wits.
  • Power: Supernatural awareness and abilities.
  • Size: Physical height, weight, mass.
  • Strength: Brawn, muscles, physical force, lifting, carrying.

…plus:

  • Move Rate: For humans, defaults to 10, meaning 30 meters (100 feet) per combat round.
  • Damage Bonus: Amount added or subtracted to hand-to-hand and melee damage.
  • Hit Points: Tracks physical damage. If taking half hit points in one hit, suffer a Major Wound. Unconscious at 1 or 2 HP, dead at end of next round at 0 HP.
  • Fatigue: Tracks physical stamina. Lose 1 per round of strenous activity (fighting, climbing, etc.). Exhausted at 0 or less, disadvantage on all tasks. Unconscious are -Fatigue value.
  • Sanity: Tracks mental damage. If losing 5 or more Sanity from one check, make an Intelligence saving throw. One success, suffer Short Temporary Insanity for 1d10+4 rounds. If failing INT save, suffer Longer Temporary Insanity for 1d10x10 hours. If losing 1/5 of total Sanity in one hour, suffer Indefinite Insanity. Permanently insane at 0 Sanity.
  • Power Points: Used to fuel supernatural powers. Cost varies by power.
  • Luck: Points to add or subtract to dice rolls, up to 10 per roll.

Recovery rates

  • Hit Points: Immediately regain 1d3 HP if given First Aid (one time only). If no Major Wound, heal 1 HP per day. With a Major Wound, make a Constitution save at the end of each week to regain 1d3 HP. If hospitalized, automatically regain max (3 HP) if making the CON save.
  • Fatigue: Regain 1 per minute of rest/low activity.
  • Sanity: No natural recovery, but for each month of successful psychotherapy, regain 1d3-1.
  • Power Points: Regain 1 point per hour of sleep, or 1 point every two hours while awake.
  • Luck: At start of each play session, roll d100. If equal to or over current Luck, gain 2d10+10 Luck. If under Luck, gain 1d10+5.

TASKS

Basic Tasks: Roll equal to or under characteristic or skill rating on d100.

  • Roll equal to or under your rating is a success.
  • Rolling under 1/5 your rating is a special/hard success.
  • Rolling under 1/20 your rating is an critical success.
  • Rolling 01 to 05 is always a critical success, while 96 to 00 is a critical failure/fumble. (The official rules nuance this a bit per the above guidelines.)

Opposed Rolls: Each side makes a task check.

  • If both fail, no result.
  • If one succeeds and other fails, the successful result wins.
  • If both succeeds but one has a better success (i.e. special/hard over regular), the better result wins.
  • If both succeed at the same degree, the side with the higher base rating wins.

Extended Rolls: Requires a specific number of successful checks to complete the task. Each check takes a number of rounds, minutes, hours, days.

Automatic Skills: If not listed on a character sheet, a character still has the following base chance of success for the following skills:

  • 15% … Appraise
  • 25% … Brawl
  • 40% … Climb
  • (DEX/2) … Dodge
  • 20% … Drive (Automobile)
  • 20% … Firearm (Pistol)
  • 25% … Firearm (Rifle)
  • 30% … Firearm (Shotgun)
  • 30% … First Aid
  • (INT+POW)/2 … Gaming/Gambling
  • 25% … Grapple
  • 10% … Hide
  • (EDU or INT) … Language (Own)
  • 25% … Listen
  • 25% … Jump
  • 25% … Melee Weapon (light, like Knife or Quarterstaff)
  • 15% … Melee Weapon (medium, like Axe or Sword)
  • 10% … Navigate
  • 15% … Persuade
  • 15% … Repair (Any)
  • 25% … Research (Any)
  • 10% … Sense
  • 25% … Spot
  • 10% … Stealth
  • 15% … Status (General)
  • 25% … Swim
  • 10% … Teach
  • 10% … Track
  • 25% … Throw

In the early 21st century…

  • 15% … Technical (Computer Use)

In a far future/sci-fi setting…

  • 15% … Technical (Computer Use)
  • 15% … Technical (Vaccsuit/Spacesuits)

COMBAT RULES

Combat rounds are 12 seconds long; five rounds equals one minute. Each round follows in four phases:

  • Statements: In descending order of characters’ Dexterity (highest declares first), players state the intent of their characters actions. A character may delay to the end of a round (at DEX 1), but if conditions are not met then, action is lost.
  • Powers: Instantaneous powers (magic, psionics, mutations, superpowers) activate in descending order of characters’ Intelligence.
  • Actions: In descending order of characters’ Dexterity (highest declares first), players roll dice to resolve their characters actions as needed. In combat, targets may make defensive rolls (Parry with weapon or shield, or Dodge).
  • Resolution: Measure outcomes as needed.

Actions and moves allowed during a turn:

  • Move up to 5 meters (19 feet) at full effective Dexterity.
  • Move up to 5 meters and make one attack roll or other noncombat action.
  • Move up to 5 meters while disengaging (knockback enemy and retreat, or run and give enemy one free attack at disadvantage that cannot be parried/dodged).
  • Move 6 to 15 meters (20 to 50 feet) at 1/2 effective Dexterity.
  • Move 16 to 30 meters (51 to 100 feet) at 1/4 effective Dexterity.

Defensive actions:

  • First parry or dodge of turn (full skill rating).
  • One bonus parry or dodge at full skill is Fighting Defensively (no attacks).
  • Second parry or dodge (-30% skill).
  • Third parry or dodge (-60% skill).
  • Fourth parry or dodge (-90% skill).

Missile attacks may not be parried.

Attack results:

  • Critical Success: Maximum damage unless target has critical success with Parry or Dodge, in which case attack misses.
  • Special/Hard Success: Roll damage unless target has critical/special/hard successful Parry or Dodge.
  • Success: Roll damage unless target has successful Parry or Dodge.
  • Failure: Attack misses.
  • Critical Fail/Fumble (House Rule): Fall prone, break weapon, or suffer Disadvantage for 1d3 rounds.

Burst fire and full autofire (machineguns and the like):

  • Burst: +30% to attack; if success, 1d4, 1d6 hits (player’s choice), half ammo expended.
  • Autofire: +60% to attack; if success, 1d8, 1d10 hits (player’s choice), ammo fully expended.

Shields versus missile fire:

  • Half/Small Shield: 15% chance to block.
  • Full Shield: 30% chance to block.
  • Large Shield, or kneeling behind Full Shield: 60% chance to block.
  • Kneeling behind Large Shield: 90% chance to block.
  • Ignore shield if missile attack scores a Critical or Special/Hard success.

Armor Value (AV) is subtracted from damage per hit:

  • AV 0: Normal clothing, no protection.
  • AV 1: Hide, soft leather, heavy clothing.
  • AV 2: Hard leather.
  • AV 4: Modern bulletproof vest, flak jacket.
  • AV 5: Ring mail.
  • AV 6: Scale mail.
  • AV 7: Chainmail, half plate.
  • AV 8: Full plate, sci-fi light assault armor.
  • AV 10: Sci-fi assault armor.
  • AV 12: Modern riot gear.
  • AV 14: Sci-fi light powered assault armor (battlesuit).
  • AV 16: Sci-fi heavy powered assault armor (battlesuit).

SANITY NOTES

Make/fail Sanity check…

  • 0/1 … Suffer a shock or extreme surprise.
  • 0/1D2 … Surprised to find mangled animal carcass.
  • 0/1D3 … Surprised to find human corpse.
  • 0/1D3 … Having a close brush with death (near fall, car crash, being shot or stabbed, etc.).
  • 0/1D3 … Surprised to find severed body part.
  • 0/1D4 … Seeing a stream flow with blood.
  • 0/1D4 … Unintentionally cause the death of another.
  • 0/1D4 … Casting “black magic.”
  • 1/1D4+1 … Finding a mangled human corpse.
  • 0/1D6 … Awakening trapped in a coffin.
  • 0/1D6 … Witnessing a friend’s violent death.
  • 0/1D6 … Committing willful murder.
  • 0/1D6 … Seeing a monster.
  • 0/1D6 … Casting powerful “black magic.”
  • 0/1D6 … Seeing something supernatural or patently impossible.
  • 1/1D6+1 … Meeting someone you know to be dead.
  • 0/1D10 … Undergoing severe torture.
  • 0/1D10 … Casting supremely powerful “black magic.”
  • 1/1D10 … Seeing a corpse rise from its grave.
  • 2/2D10+1 … Seeing a gigantic severed head fall from the sky.
  • 1D10/1D100 … Seeing a primordial god of Chaos in monstrous form.

HOUSE RULES

Quick-and-Dirty Results: Any roll under skill by 25% or more is a Special/Hard success. A roll of 01 to 05 is always a Critical Success.

New Skills: Several new skills added to character options. Their use is either self-explanitory or up to the creativity of players.

Language (Own): Use either Intelligence or Education as default.

Advantage and Disadvantage: Fully roll both dice twice and use the better or worse result.

Lucky Rerolls: Expend 10 Luck points to reroll a dice result, using the better result. Can be used to help allies or hinder enemies, but only if the character is aware of the task in progress (can see the action).

Teamwork: Each character rolls against the highest level of skill from among the group.

Damage, Hit Locations, Piecemeal Armor: Ignore unless rolling for a Major Wound result.

Custom Major Wound Table: When a single hit does damage worth half a target’s maximum Hit Points, roll d100. (Characters may spend 10 points of Luck to reroll on this table if necessary.)

  • 01 to 10 … Legs injured. Disadvantage on Dexterity-based tasks, and move rate halved. Effect ends when HP fully recovered.
  • 11 to 20 … Facial scars. Disadvantage on Charisma-based tasks. Effect ends when HP fully recovered.
  • 21 to 30 … Hand or arm injured. Disadvantage on Strength-based tasks. Effect ends when HP fully recovered.
  • 31 to 40 … Internal chest wound. Disadvantage on Constitution-based tasks, and move rate halved. Effect ends when HP fully recovered.
  • 41 to 50 … Concussion damage. Disadvantage on Intelligence-based tasks. Effect ends when HP fully recovered.
  • 51 to 60 … Loss of one or both legs. Disadvantage on Dexterity-based tasks, move rate halved. Permanent.
  • 61 to 70 … Facial mutilation. Disadvantage on Charisma-based tasks and preception tasks (Listen, Spot, Sense). Permanent.
  • 71 to 80 … Loss of hand or arm. Disadvantage on Strength-based tasks. Permanent.
  • 81 to 90 … Injury to vitals. Disadvantage on Constitution-based tasks, move rate halved. Permanent.
  • 91 to 00 … Massive mutilations. Permanently lose 10 points each from Charisma, Dexterity, and Constitution. If any one characteristic drops to 0, character dies.

Custom Temporary Insanity Table: When a character loses 5 or more Sanity from a single incident or failed Sanity check, make an Intelligence saving throw and roll d100. On a failure, character represses event and will have no memory of it. One a success, roll on the Short Temporary Insanity table. On a critical success, roll on the Longer Temporary Insanity list. (This rule comes from Call of Cthulhu, 6th Edition.)

Short Temporary Insanity: If a single check’s Sanity loss was less than half a character’s full Sanity, the effect lasts 1d10+4 rounds (about 1 to 2 minutes).

  • 01 to 10 … shaken confidence and dread, Disadvantage on all tasks roll
  • 11 to 20 … fainting or screaming fit, Disadv. on all task rolls
  • 21 to 30 … flees in panic at full move rate
  • 31 to 40 … hysterics or emotional outburst (laughing, crying, etc.)
  • 41 to 50 … babbling or stream of incoherent rapid speech
  • 51 to 60 … homicidal mania (enemies or “those responsible” must be killed)
  • 61 to 70 … hallucinations or delusions, “this can’t be happening”
  • 71 to 80 … character’s will collapsed, does what others say to do
  • 81 to 90 … bizarre behavior (eating dirt, tearing off clothing)
  • 91 to 00 … catatonic stupor, rigid and immovable

Longer Temporary Insanity: If a single check’s Sanity loss was equal to or greater than half a character’s full Sanity, the effect lasts 1d10x10 hours (about a half day to four days).

  • 01 to 10 … amnesia, no memory of family and friends or mental skills
  • 11 to 20 … severe phobia, sees/fears object of obsession everywhere
  • 21 to 30 … hallucinations, cannot tell reality from imagined senses
  • 31 to 40 … taboo behaviors (blasphemy, refusing to clean oneself, compulsive lying, laughing at tragedy)
  • 41 to 50 … obsession that only a specific person, place, or object can “keep me safe”
  • 51 to 60 … uncontrollable tics, tremors, cannot communicate in speech or writing
  • 61 to 70 … psychosomatic blindness, deafness, or inability to use arms or legs
  • 71 to 80 … psychosis (hears voices, convinced of delusional ideas)
  • 81 to 90 … paranoia, “everyone is trying to get to me now”
  • 91 to 100 … nonstop compulsive activity (washing hands, walking in circles, checking on supplies or door locks)