Cortex Prime Roleplaying System

Magic Vacuum Design Studio

by: Cam Banks


Cortex Prime is a highly modular analog game system that focuses on storytelling and the ability to switch out blocks of core rules like Lego bricks. With a very basic primary set of rules for running the game, mechanics, and character creation, players are able to tell any kind of interactive story they desire in any genre they can imagine. All you need is pen or pencil, paper, and d4 through d12 to play.

About the Author

Cortex Prime was developed by Cam Banks, a long time analog gamer and designer out of New Zealand. He has worked on Dragonlance, Marvel Heroic Roleplaying, and the Cortex System. Cam’s start into analog game development began as a kid when he wanted to make a G.I. Joe roleplaying game using the Dungeons and Dragons rules. Modifying that led to many other modifications over the next thirty years. His work has culminated in the Cortex Prime Roleplaying System.


On the surface, the mechanics of the Cortex system are pretty simple. Roll a number of dice, add any two dice to determine the outcome against an opposition roll or difficulty. Players then choose a third die for its type, not its result.  This “effect die” determines the extent of the effect. So an effect die that is a d6 is important, not the fact that it rolled a 5 this time around.

Once you get past this simple idea, though, the system grows pretty complex. Choosing which dice are included in the roll is not just varied, its variability varies by which mod you choose to include in your campaign. The variations are so many its difficult to write about them in this short post. I will give one example here to give the barest idea of what is going on, but please understand this is one of vast many possibilities.

First, the GM will choose one die based on the difficulty of the situation the character faces. This die will be a d4 to a d12 in size. Then, they will pick up more dice based on traits from the location, opposing characters, and events going on in that scene. The GM can even add additional d6 to the pool if they feel the need to increase the danger faced by the PC. The GM rolls and chooses two dice rolls to set the difficulty the player character has to overcome once the dice pool is set. After that, the player selects a similar pool of dice based on their own traits, SFX, and special assets or conditions. If they beat the GM’s roll, it’s a success. If not, it’s a failure.

Rolling a 1 on any die is considered a spoiler.  The GM then uses spoilers to affect things related to the story or mechanics. Any 1 on a die means that die may not be used toward the total or as the effect die. If all 1’s are rolled, that is a botch and is equivalent to a critical failure in other systems.


There is so much more to the mechanics than this little bit, but the last thing I’ll touch on here is the idea of the mods themselves. Both published and homebrew mods are available.  Mods are sets of rules around a concept or concentrated group of concepts within the game.  Players can insert or remove mods as desired. Some include mods that change:

  • names or the way players view the die rolls,
  • number of dice counted from the pool,
  • the way the game treats effect dice
  • how to determine difficulty and opposition rolls,
  • the use plot points,
  • independent dice pools for a host of different uses that the GM and/or players can draw from,
  • and many, many, many more…

The Cortex Prime system is a Homebrewer’s paradise.

Races, Bestiary, and Beyond

Given the absolute modularity of the game, there is no included races, bestiary, equipment, crafts, or other material. Players generate these for their individual game to play with or against as needed.

Character Creation

Players design their characters much the way a famous actor might prepare for different movies in different genres. Players use at least two trait sets.  These sets represent a number of dice that can be added to a dice pool. The core rulebook offers some premade sets for genres such as Super Heroes, Romantic Fantasy, and Heist Action, but truly it is up to the players to decide which trait sets they wish to incorporate for their game. Trait sets listed are attributes, skills, affiliations, relationships, powers, roles, and values. However, the modular nature of the game can include other traits or switch traits around as needed.

From there, players choose how to distribute the dice across the traits in any set. For example, in the Attribute set they might put a d4 in Strength, a d6 in Constitution, a d10 in Dexterity, a d12 in Intelligence, a d8 in Wisdom and Charisma IF their Attribute set were modeled after the D&D gaming system. Cortex Prime allows for other Attributes instead of these (e.g. Courage, Guile, Reason, and Vigor instead or in addition to).  I chose these classic Attributes because I am most familiar with the D&D rule system.

After the trait sets are chosen, the player chooses a number of special effects (SFX). These work something like Feats but are limited to special circumstances. These SFX can alter the game mechanics in multiple ways including increasing the type of die rolled for a trait, removing a die from the opposing dice pool, earn plot points, and many others.

Last of all, players choose Specialties and Signature Assets. These are skills or talents they are especially good at and recognized for in the game world or equipment that is peculiar to their character. These add to both the story and the mechanical strength of the character in multiple ways.

Overall Response

Cortex Prime is the culmination of many years of hacking older analog systems, homebrewing, and just good old experience around the table with friends. For those who like complexity, versatility, and doing things exactly the way you think they ought to be done, Cortex Prime is your El Dorado.

Rating – G+

If you’d like to catch the interview by Game School, you can check it out here:

To find out more about the Cortex Prime game go to:



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