Text in green is information that is still to be decided.


Twelve is an open source Customizable card game where any user can create their own cards following a set of rules. 

Cards can be collected, traded and played.


Card dimensions- 2.5 inches x 3.5 inches (Standard playing card dimensions)

Card types- Character cards and Effect cards.

Character cards represent a character or concept, and are used to fight, while Effect cards are used for other kind of actions that alters the game’s elements.

Card creation

Character cards

This card represents a character,
Every character card has 3 stats: Attack, Health and Special. When creating a card, players have up to 12 points they can divide in between each stat as they please. They do not need to use all 12 points, and 0 is a valid value.

Obligatory parts

  • Title- The name of the card. Usually the name of the character

  • Art- The visual aspect of the card! Can occupy as much or as little as the creator decides, as long as the stats are legible. There’s no set design in order to give artists liberty

  • Attack- The damage they will cause to other character cards. 

  • Health- Damage characters are able to take

  • Special- Max value the sum of Effect cards affecting this card can reach. 

For example, a card with Special 5 can be combined with a 3 and 2 Effect cards, but not with two Effect cards with a value of 3 each.

Optional parts

  • Passive ability-If a character card has a passive ability, a specific amount of points must be dedicated to it, reducing the amount of total points that can be applied to the stats. The passive skill can have up to four effects: Block, Heal, Buff, Debuff, with the points that were saved for the passive ability divided between each of the effects chosen.
    Unlike Special, passive abilities do not run out of points once used and can be used once a turn in any target (unless stated otherwise). Cost is subject to the same rules as Effect cards.

  • Flavor text- This is just optional flavor text about the concept or the artist… or anything the creator feels like, really. It does not have any effect in-game.

  • Artist- Information about the artist. Optional, but highly recommended.

Effect cards

This card represents a concept, item or event, and affects one or more elements of the game. 

Value calculation

Effect cards have a single value. This value can be visible (present in the card) or invisible (not present in the card).  An Effect card’s value is calculated depending on the number of elements it affects in-game.

An Effect card’s max possible value is 12. 

Visible value can not be 0. Invisible value can only be 0 as a result of value decrementing variables (f.ex dice)

Invisible value

The value does not need to be present in the card and can be calculated in-game. This can result on an Effect card’s value being different each time (if the number of turns is up to the player, for example) In the case the value is present, the player must abide by it.

Cost incrementing

  • Active Card structure- When interacting with a card, each part of the card has its own cost depending on the change.

    • Attack changes- The value of a character’s attack is changed. +1 value for each point (absolute value)

    • Health changes- The value of a character’s health is changed. +1 value for each point (absolute value)

    • Special changes- The value of the character’s Special is changed. +1 value for each point (absolute value)

    • Name-The card’s name is changed or taken into consideration. +1 value for each card whose name is affected. 

    • Passive ability change-+Value equal to the sum of the value of the passive abilities affected

    • Extra cards affected-+1 for each card beyond the card whose special is being used to fuel this effect.

  • Opponent’s field- Crossing over into the opponent’s field increments any action’s value by 1.

  • Turns- The amount of turns over 1 that the Card will be in effect. +1 value for each turn after the one in which this Effect card is played.

  • Action changes- +1 for each change that would or would not happen without this Effect card. This includes attacks, passive abilities or its denial.

Example- Opposing player’s character attack is nullified this turn (Value=2)

  • Card piles +1 for each card pile affected that you own, and +2 if it belongs to your opponent. Number of cards and Placement changes still counts in addition to this.  The card piles are ‘Deck’, ‘Hand’ and ‘Discard pile’

  • Quick effect-Cards in response to Effect cards. Can be played during the opposite player’s turn.The value is 1*every card affected, including your own, even if they are defending 


Cost decrementing 

  • Sacrifice- -1 value for each card that is moved to the discard pile. These can only be of your own.

  • Conditions-There can be specific conditions that if true or false, will cause an effect to take place. Condition has to be related to a part of the game that can be altered. F.ex. # of character cards in game, # of character card’s attack. The cost is reduced by 2 by every requirement.

  • Dice- Dice might be involved with the conditions. In that case, the following rules apply:

    • -1 value for every 6 faces the dice has. 

    • +1 value for the amount of results that are considered positive.

    • -1 value for the amount of results that are considered negative

Extra examples

  • Own character’s attack and health are switched for 2 turns. Value =3
    +1Attack change, +1 Health change, +1Extra turn

  • Draw two cards. Value=4
    +1 Deck(regular), +1 Deck (hand), +2 Card movement

  • If a card’s attack is 3, that card is defeated. Value = 1 or 2
    +1 Card affected, +1 Card movement, -1 Condition. +1 if card is opposing.

  • For each character card that you’ve lost this turn, draw 1 card. (Two cards are lost so far. This card is being used as a quick one) Value =5
    +1Deck (own), +1 extra card affected, +2 Cards moved +1Quick effect


Game can be made between any number of players, but the 2 is the recommended amount.

First player is decided at random.Or by being very nice and agreeing with each other.

Player’s turn


Each player can have a deck from 24 to 48 cards. 

When starting, each player draws 6 cards.

Player turn is decided by chance. Or by being very nice and agreeing with each other.


  • Point capture mode- A pool of points is agreed on (must be 12 or multiple of 12). Each time a character card is defeated, the player whose character card attacked earns a point. The first player who earns the most points wins, In the case of a tie, players engage in an extra run.

  • Surviva model-Each player has 12 or a multiple of 12 life points. Each time a character card is defeated, the player loses the difference between the other character’s attack and their character’s health. The first player who loses all their life points loses.

  • Labyrinth mode- The cards create a structure the effects and attacks have to cross, reducing and increasing depending in positioning.

  • Free mode-Players may come up with a different gameplay mode if they please. I mean, we are not going to stop ya.

Player’s turn

01-Turn starts with the player drawing a card.

01- The player can place a single character card per turn.

02-Effect cards are applied as desired as long as the active characters have Special stats that can sustain them. Every time an Effect card is used by a card, place a number of tokens on that card equal to the value of the Effect card. 

03-Player can use their character cards to attack. For each point of damage the character causes, place a token in its target. If the target’s damage is equal or superior to its health, this target is considered defeated and it’s discarded. 

During this phase, the opposing player can play a quick effect card if it applies.This does not apply during the first turn.

04- Turn ends.

Card actions


Once per turn. The player may use their character cards to attack the other player’s character cards.


When a character card is attacked, place tokens equal to the damage it received. If a character is damaged beyond its health, this character card is considered defeated and it is discarded.


You may spend a character card’s Special to use Effect cards. When you use the Effect cards, place a token in this character card. The amount of Special tokens can not exceed the Special of a character card. Special is not recovered in between turns.


Twelve mixes the ideas of adoptables, MUGEN and business cards into a highly collectable hobby.


Every person is free to make their cards of any kind! You can turn your OCs into cards, or implement concepts from original works. For fun and for promotion.


The mix of art, promotion and the push for artist credit transforms Twelve cards into an alternative to business cards. 


As a collector, imagine having whole decks of your small pieces of your favorite artists’ cards! If you are familiar with adoptables, it’s a similar concept!


It could even become a merch idea. People could have booster packs in their personal stores, or as pluses in other purchases, similar to collaborations TCGs have with companies, but at a smaller scale.

The small size and weight of single cards also allows for the usage of letters instead of packages, which will reduce the price of shipping, making this a very approachable product internationally.


This game is thought to be a casual game due to its infinite amount of variables. Even if the creation rules are intended to keep balance, there’s always the possibility of exploits.


Do you want to make your own cards? Here’s some resources for you!

  • Custom Game Cards Make sure to choose ‘Poker size’, which is the standard size! You can make decks containing 16 to 612 cards, with minimal orders of 1-5


While anybody can create cards as they please, any concepts reflected in the cards still belong to the original artist. The rights extend only to the usage of the cards themselves

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