Jazz 4.0:JazzCore

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JazzCore is the base rule set for Jazz. For games set in the "real" world, JazzCore should be sufficient. For more outlandish games, additional rules may be helpful (or you can just wing it).


What you are reading now is JazzCore (or just "Jazz"), the basic structure of Jazz. The "genre modules" for Jazz (i.e. JazzApocalypse, JazzSorcery, JazzVoodoo, etc.) have yet to be written. In theory, you can use Jazz for post-apocalypse games, sword-and-sorcery games, and so on, but until the genre modules are written, you'll need to do a lot of prep work yourself. There is still a lot of room for heroic characters: extraordinary strength and balance, a preternatural sense for danger, etc., are easily done. But for the time being, more blatant violations of what we tend to call reality would have to be handled case-by-case by the GM and players.

Character checklist

  • Aspects: one primary, and one or more secondary
  • Health pool: equal to survival aspect bonus
  • Weird pool: equal to weird aspect bonus
  • Complication (optional)


An aspect is a particular facet of the character, usually expressed as an adjective followed by a noun. For example, "absent-minded genetic engineer", "intuitive occult librarian", and "hard-drinking sniper" are all aspects -- and could all be aspects of the same character. If a specific task could apply to more than one of a character's aspects, the player may roll whichever aspect has the highest bonus.

Listed below is a table of typical aspects for a relatively realistic modern-day game. For primary aspects, choose one word from Column 1, and one word from Column 2. Do the same for secondary aspects, or choose one from either column. Or make up your own aspects (with the GM's help and consent). Genre modules will offer additional typical aspects.

Keep in mind that the combinations listed here are minimalist -- you can be and probably should be more creative than this. For example, rather than "streetwise driver", your character could be a "former getaway driver". Rather than an "analytical mystic", your character could be a "strait-laced hereditary witch".

Table: Typical aspects
Column 1
Lower class
Upper class
Column 2
Bounty hunter
Martial artist
Police officer
Stage magician

The first aspect a character has is her "primary aspect". The character's primary aspect is a broad description of her basic character type. A character's primary aspect should be deliberately broad, to cover a wide range of skills and abilities. The character's primary aspect often has the highest bonus among the character's aspects, but this is not mandatory. Aspects after the first are "secondary aspects". Secondary aspects may be relatively specific, if the player prefers (e.g., "drunkard", "scientist", "gunslinger").

The most important thing about aspects is not that they are effective in combat or useful in every possible situation. You could make up a "tough-as-nails soldier" who is a "brilliant strategist" and "strong-willed", but a group of such characters is going to be as dull as dishwater. Combat is a small part of a role-playing game. Make your character someone interesting to have around. You will have more fun, and the people playing with you will have more fun.

Also, keep in mind that not all aspects actually mean the same thing. One soldier may know how to drive tanks and rebuild engines, but know nothing about logistics. Another soldier may be able to set and disable explosives, but know nothing about artillery. You (with the GM's help and consent) decide who your character is and what they can do -- and what they can't do. Just because your character is a British secret service agent does not mean that she knows everything about everything.

Weird aspects

Some aspects grant a character powers beyond the realm of what most people can do, no matter how high their aspect bonuses are. These abilities might be the result of magic, mutation, specialized training, or some other source. When you record a "weird aspect" on your character sheet, note it with an exclamation point after the aspect bonus (e.g., "+3!").

Weird aspects usually work just like other aspects. However, the character can use the weird aspect to perform extraordinary actions a limited number of times. If a character uses their weird aspect to perform an action which is truly extraordinary or supernatural, the character's weird pool is reduced by one. When the character's weird pool is depleted, they can't perform any more truly extraordinary actions until they have rested, but they can still perform weird actions which are not truly extraordinary or supernatural.

Simply attacking a single target or defending against an attack is not usually considered extraordinary, since anyone with ordinary equipment could do the same thing.

Fiction level

The aspect bonus is the number associated with the aspect. The total number of bonuses to be allocated among the character's aspects and the maximum bonus of a single aspect are dependent on the "fiction level" of the game being run. The more outlandish the game, the more bonuses the character may distribute among her aspects, and the higher the bonuses of those aspects may be.

Table: Fiction level
Fiction level Total bonuses Max bonus
Mundane 4 +2
Exceptional 6 +3
Elite 8 +4
Heroic 10 +5
Legendary 12 +6
Mythic 14 +7

You can see from the total bonuses and max bonus permitted at each fiction level that a character will have at least two or three aspects. This should allow enough aspects for anyone to describe a well-rounded, interesting character.

Areas of expertise

Now that you have your aspects selected, it would be helpful to know what they entail. Think of a number of short phrases equal to the aspect bonus, describing what the character can do that other people normally can't (or can't do as well). For example, a "former getaway driver (+4)" might have these four short phrases:

  • Casing the joint
  • Hot-wiring cars
  • Exceeding the speed limit
  • Evading pursuit

Put it all together, and you have:

Former getaway driver (+4): casing the joint; hot-wiring cars; exceeding the speed limit; evading pursuit

Your aspect is not limited to these listed abilities, of course, but they should give the GM a solid idea of the kind of things you expect your character to be able to do.

Universal aspects

Universal aspects are things generally known by everyone in a specific culture or time period. Universal aspects could be commonplace abilities, like the ability to drive a car or use a telephone, or it could be a straightforward ability that everyone can attempt even without training, such as brawling or assembling a chair from Ikea. Every character in a given setting is assumed to have a +1 bonus in all universal aspects appropriate to that genre. These do not need to be written on the character sheet.

Missing aspects

If a character is in a situation where she has no appropriate aspects, she can normally roll to attempt the task, but she adds none of her aspects, and the difficulty may be higher than usual. Only if the task is truly extraordinary, requiring specialized training or experience to even make an attempt (however feeble that attempt might be), would the character be unable to roll at all.

Health pool

Health is a measure of how much abuse a character can take before she is out of the fight. The character's health pool is equal to her most survival-relevant aspect bonus (e.g., +4 = 4 health).

"Survival-relevant" does not necessarily reflect combat training or sheer physical prowess (although of course it can). A "street-smart orphan" and a "slippery bureaucrat" also have survival skills.

Weird pool

Weird is a measure of how often a character can use her weird aspects to perform extraordinary actions. The character's weird pool is equal to her weird aspect bonus (e.g., +2 = 2 weird).

Each time a character uses a weird aspect, their weird pool is reduced by one. When the character's weird pool is depleted, they can't perform any more truly extraordinary actions until they have rested.

Using a weird aspect does not always reduce the character's weird pool. If the same sort of task could be performed by someone with a non-weird aspect ("thief", "acrobat", "sharpshooter", etc.), then the action does not reduce the character's weird pool. For example, picking the lock on a door or planting a computer virus would not normally reduce the character's weird pool, but planting a virus on a computer from the hallway outside a locked computer room probably would. Even a character with a depleted weird pool can perform weird actions which are not truly extraordinary or supernatural.

Complication (optional)

A complication makes the character's life more difficult, and thus more interesting. A complication should be something meaningful, preferably something related to the character's personality (e.g., "relentlessly curious", "driven to protect humans from nonhumans", "prone to reckless overconfidence"). If a weird aspect plays a major role in the character's background, the character's complication can pertain to this aspect (e.g., "must have hands free to cast spells", "must abide by complex set of taboos", "weird pool only replenishes in a cemetery").

If a character's complication prevents them from making an important roll or otherwise stops them from doing something they want to do, the character gets an advantage die which may be used later at a time of the player's choosing (advantage is covered below).

NPCs can have esoteric, plot-dependent complications, such as "health pool only replenishes if the character sleeps on their native soil".

Some genre modules will offer a list of typical complications. The player may choose a complication from that list, or make up her own (with GM approval).

Rolling dice

When a character uses an aspect, and the outcome is either contested or there is some random element involved, the player rolls two six-sided dice (hereafter referred to as "2d6"), adds them together, and then adds their relevant aspect bonus. This roll is compared against a difficulty number the GM assigns (or a roll the GM makes, if someone is actively opposing the character). The attempt succeeds if the player's roll equals or exceeds the assigned difficulty (or the GM's roll).

Table: Difficulty examples
Difficulty Examples
8 Easy Understand and modify simple machines, operate current technology
10 Challenging Understand and modify current technology, operate advanced technology
12 Demanding Design and build current technology, understand and modify advanced technology
14 Frustrating Design and build advanced technology, operate advanced alien technology
16 Nigh‑impossible Understand and modify advanced alien technology

There is no need to roll for routine tasks at all: characters automatically succeed at routine tasks. Similarly, there is usually no need to roll if there is no penalty for failure and/or no time limit: it might take months, but the character will succeed eventually.

Weird aspects can achieve things that no normal aspect, regardless of its bonus, can do. The difficulty of such endeavors depends on how grandiose the desired effect is and its impact on the game. The GM must decide on a case by case basis how heavily to weigh these concerns.

Table: Weird difficulty examples
Difficulty Game impact
8 Easy Teleporting an individual a few meters. Getting a hint to a problem. Changing the color, cleanliness, or cosmetic appearance of an existing device or object. Altering the terrain or environment in the local area in a minor, unobtrusive way. Reassuring or commanding a friendly animal. Restoring one health to an unconscious character, waking them up.
10 Challenging Teleporting an individual across town, or an entire group a few meters. Getting a valuable clue to a problem. Controlling the function or integrity of an existing device or object, such as unlocking a door, operating a magnetic crane, or repairing an automobile. Altering the terrain or environment in the local area in a way that does not seem out of place (for example, making it snow in New York, or making it rain in Virginia). Befriending and gaining the trust of an animal. Restoring up to one-half of a character's health pool.
12 Demanding Teleporting an individual to the other side of the world, or an entire group across town. Getting a straight answer to a simple question. Controlling the function or integrity of an existing structure, such as shutting off the power in a building, or sending the same message to every television, telephone, and computer screen in a locked-down facility. Substantially altering the terrain or environment in the local area (a city block, or a neighborhood). Creating a small but loyal familiar. Deceiving or manipulating a group of unnamed characters. Restoring a character's health pool to full.
14 Frustrating Teleporting an individual to a distant world or dimension, or an entire group to the other side of the world. Getting a valuable clue to a complex mystery. Drastically and unnaturally altering the terrain or environment in the local area, or substantially altering the terrain or environment in a much wider area (an entire city, or a long stretch of coastline. Creating a ferocious animal protector or an obedient but nonsentient servant. Restoring one health to a dying (or very recently dead) character, stabilizing them.
16 Nigh‑impossible Teleporting an entire group to a distant world or dimension. Getting a simple, direct answer to a complex mystery. Creating a living, intelligent being with its own independent existence. Restoring one health to a dead character, bringing them back to life.


Conflict is usually physical combat (such as a gunfight), but it could also be a mental contest (such as a contract dispute), or a social struggle (such as a domestic argument). It could also be something stranger.

Initiating conflict

If a character wishes to initiate a conflict, each player rolls 2d6 for their character, and the GM rolls 2d6 for each antagonist. If one or more characters gets the drop on their opponents (a surprise ambush, for example), the characters with the advantage each get an advantage die on their initiative roll. Actions proceed each round from highest roller to lowest, with each character getting an action. When everyone has had the opportunity to take an action, the highest initiative goes again, and so on until the conflict has ended.

Resolving conflict

If a character wishes to use her action to attack, the attacker rolls 2d6 plus her relevant aspect bonus. The defender also rolls 2d6 plus their relevant aspect bonus. If the attacker's roll equals or exceeds the defender's roll, the defender's health pool is reduced by one. If a character's health pool is depleted, they are out of the fight: they can no longer take actions. If it's a physical combat, they are probably unconscious. The winner may choose what happens to the loser at that point.

A character may only attack once per round, but a defender may roll as many times as she is attacked.

Teaming up

Multiple characters can work together on a problem to increase their effectiveness. All of the characters working on the problem make an aspect roll as usual. The total number of characters working on the problem is added to the highest roll (all other rolls are discarded). For example, two people working together add two to the highest roll, even if the lowest roll is an abject failure.

In combat, the total number of attackers is added to the highest attacker roll (all other rolls are discarded). This does not make the attack more deadly, but it does make the target a lot easier to hit.

Some problems might benefit from a multidisciplinary approach. For example, disabling an alien doomsday weapon would obviously benefit from engineering expertise, but a keen understanding of alien psychology or linguistics could also be helpful. This allows characters with different aspects to combine their efforts to accomplish the task.

Unnamed characters

If an attacker's roll equals or exceeds an unnamed defender's roll, the unnamed defender is out of the fight. Unnamed characters are typically security guards, common thugs, or innocent bystanders.

Advantage and disadvantage

Some situations grant an advantage to a character. If the character has an advantage, roll one extra die (3d6 rather than 2d6). If the character has a disadvantage, roll one less die (1d6 rather than 2d6). It is possible to have an advantage die and a disadvantage die at the same time. If the character has an advantage die and a disadvantage die, they cancel out, and it's just 2d6.

It is not possible to have more than one advantage die or more than one disadvantage die.

Karma (optional)

With the GM's consent, a player can trade good fortune now for bad fortune later, or vice versa. If a player voluntarily fails at something their character genuinely wants to do, or permits their character to suffer a painful or humiliating setback, the GM can grant the player "positive karma". A character with positive karma has one advantage die, which the player may use on any one future roll.

Conversely, if a character desperately needs to succeed on a roll, but they don't, the GM can grant the player an advantage die on the roll. If the roll is then successful, the GM then assigns the character "negative karma". A character with negative karma has one disadvantage die, which the GM will impose on one future roll -- generally when it matters most.

If a character has both positive karma and negative karma, they cancel out, and the character's karma returns to neutral (having neither an advantage die nor a disadvantage die). It is not possible to have more than one positive karma or more than one negative karma.

Recovering health

Once per day, an injured character may recover half of their lost health by resting for about half an hour. After that, a character may only recover additional health by getting a good night's sleep (or its equivalent, for characters who don't sleep). Barring some gruesome disfigurement, a character's health pool will be completely replenished after a solid night's rest.

Recovering weird

Once per day, a character may recover half of their lost weird by resting for about half an hour. After that, a character may only recover additional weird by getting a good night's sleep (or its equivalent, for characters who don't sleep). Barring some particularly malicious attack on the character's aspect, a character's weird pool will be completely replenished after a solid night's rest.

Adding or improving aspects

At the end of each game session, a player may attempt to increase one of their existing aspects, or add one new aspect (with the GM's help and consent).

To improve an aspect, the player may roll a number of six-sided dice equal to the aspect bonus they want to improve. For example, if the player wants to improve an aspect bonus from +4 to +5, the player rolls 4d6. If the player rolls all sixes, then the aspect bonus permanently increases to +5. If the character increases their survival aspect bonus or their weird aspect bonus, their health pool or weird pool increases as well. An aspect bonus may not exceed the maximum imposed by the setting's fiction level, even if the player rolls all sixes.

With the GM's approval, the player may add a new aspect rather than increase their existing aspect. To add a new aspect, the player may roll a number of six-sided dice equal to the aspect bonus most similar to the aspect they want to add. (It's easier to learn things that are similar to what you already know.) If the player rolls all sixes, then they gain a new aspect at +1.


A character is assumed to have the ordinary equipment associated with their aspects. If they lose this equipment, they can still use their aspects, but they do so with a disadvantage die (disadvantage is described above).

Unusual equipment

Particularly fortunate or well-prepared characters may have access to equipment above and beyond the ordinary. For example, a "tough-as-nails soldier" with time to prepare and a few markers to call in might be able to obtain a portable rocket launcher, granting them an advantage die on their attacks as long as they have ammunition for it. Some unusual equipment might have unique effects, such as an enchanted blade which allows the player to re-roll any dice that roll ones, or a cursed amulet which makes the wearer immune to magic but which forces them to re-roll any dice that roll sixes.


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