2d20 Mod notes and basics

This is the first part of a series looking at putting together a basic, modular, generic version of the 2d20 system.

Note – the 2d20 rules system is copyright of Modiphius games. I am simply looking at pulling the basic rules out of the different games and then putting it make together.


  1. 2d20 is a great system and it would be great to have a base version to do your own hacks from
  2. Should improve the buzz and hype etc. around 2d20, driving more people to play it
  3. Would facilitate more community and community created content
  4. Which could then be added to DTRPG community content programme


  1. Allow anyone to create their own 2d20 based games using a common framework
  2. Provide the different options from heavy to light style of game
  3. Provide modules (hence Mod in title) to allow these different options


  1. Work out the 2d20 fundamentals
  2. Break down character creation in existing games
  3. Work out different forms of base character creation
  4. Look at different forms of taking action and combat
  5. Look at different forms of adversaries
  6. Look at different sub systems

Basic rules of 2d20

Rolling Dice

  1. Work out the TN. 
    1. This will be be based on a characters attributes and skills that are relevant to the task.
  2. GM sets the difficulty. 
    1. 0 to 5. 
    2. 1 is the standard difficulty.
  3. Players takes 2d20. 
    1. Player may buy extra dice 
    2. up to 3 extra
    3. By spending momentum
    4. By adding to Threat
    5. By using Special points
    6. Roll the dice!
  4. Each die that is equal to or less than the TN is a success
    1. A 20 is a complication
    2. It is possible for some dice to give 2 or 3 successes depending on focus
    3. Special points set dice to 1 and usually grant 2 successes
    4. It is possible for the complication range to be lower than 20
  5. If the number of successes is equal to or greater than the difficulty, the task succeeds
    1. If it is less than the difficulty, the task fails
    2. Extra successes beyond the difficulty are converted into momentum
  6. The GM describes the outcome of the task
    1. A player may spend momentum to improve the result further

Taking Action


When a character takes an action to complete an activity where the outcome is in doubt, they make a test. Follow the procedure for rolling dice, above.

Opposed testsWhen a character attempts to compete with, conflict with or attack another characters (PC or NPC) they both characters make opposed tests. Each character tests against difficulty 0. 

  • Active character succeeds, reactive character fails – Active character succeeds in their goal, outcome depends on the action in question.
  • Active character fails, reactive character succeeds – Active characters fails to achieve goal. Reactive character may get a benefit depending on action.
  • Both characters fail – Active characters fails to achieve goal. Reactive character gets no special benefit.
  • Both characters succeed. Whichever character achieved the most momentum on their roll succeeds. Subtract the losers momentum from the winners momentum. In the case of a tie, the Active character succeeds (but has no momentum).

Complex tests

A complex test may require multiple skill tests and in addition to a difficulty has a momentum requirement. The test is only completed when the player/s have gained enough momentum as the requirement. The test may have a time limit on it and consequences for rolling complications.



Momentum is a store of how well the PCs are doing. Players can earn momentum individually but unspent momentum is placed in a shared pool, with a maximum value (normally 6 or 7). In combat momentum drains by 1 point at the end of each round.

Momentum can be spent to achieve improved results in combat and can be spent to purchase extra dice on rolls. There may be other uses for momentum spends.

Momentum is earned from rolling more successes than the difficulty on tests


Threat is the GM currency. The GM can spend threat to give NPCs extra dice and fuel GM effects.

Threat is earned when the players buy extra dice with threat or when players roll complications which are not given immediate consequences

Threat can have a different name depending on the setting. Dark symmetry, Doom, Heat, Chaos…

Special points

The final currency is more limited. Players will start a session with 1 or 2 points. These can be used to give automatic successes (via extra dice that roll 1s) or grant additional powerful benefits. They are usually earned by good roleplaying.


2d20 characters can vary massively but have some basic commonalities:


Characters have sort of background information; social class, upbringing, place of birth, species, career.


Characters have one or two sets of attributes. These could be physical and mental attributes, skills, roles, drives or values.


Characters will have specific focuses – these are areas of skills that will give them bonus successes on tests.


Characters will have talents. These could be based on skills, roles/careers or be completely freeform. Talents can give bonus momentum, or special effects or allow characters extra special abilities.


Characters have traits that help the players roleplay. This could be an outlook, goals, drives, personality.


Characters will have sort of equipment they use.

Comments Welcome Here!

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: