Cortex Prime Review

Imagine for a moment that you’re back in May of 2017. Cannibal Halfling is six months old, and I’m still tagging all of my articles “Level One Wonk” because I felt more like a guest writer than a co-founder. I hadn’t started doing regular coverage of Kickstarter campaigns yet, so one week I decided to write an article about one that excited me: Cortex Prime. The campaign was about halfway over when the article was published, and I said some enthusiastic and somewhat hyperbolic things, like how Cortex Prime would be the next big thing after PbtA. What I’m trying to say is that I jinxed it. Cam, I’m so, so sorry.

Joking aside, this week is a special week for all of us who backed the Cortex Prime Kickstarter back in May of 2017: As of yesterday (October 20, 2020), Cortex Prime is done, it’s released, the campaign is actually over. After a number of roadblocks and obstacles, we have books in our hands and the game is actually on sale. And you know what? It was worth it. Like many other backers, I was already familiar with the Cortex system and its potential; in my case it was from Marvel Heroic Roleplaying. What Cortex Prime does is take that system and turn it into an immensely powerful toolbox, laying all the switches and dials bare in a way that GMs can actually use.

What gets me more excited about Cortex Prime than other contemporary generic RPGs is that Cortex Prime stands head and shoulders above them in terms of being a useful technical document. There are two broad shortcomings that almost every generic RPG falls into: Some, like Savage Worlds and Genesys, are not particularly more hackable than any other RPG and end up feeling like games that the setting was cut out of (which, in both of those cases, is technically true). Others, like Fate and GURPS, provide such an overwhelming amount of flexibility that entire supplements are written just about how to set them up. Cortex Prime almost falls into the latter category, but escapes it by virtue of clear writing, excellent layout, and more, better worked examples than are available in the core rulebooks of any of the above four games. What should be made clear, though, is that Cortex Prime is a toolkit, more the spiritual successor to the Cortex Plus Hacker’s Guide than any of the Cortex-based games. As much as I’m enthusiastic about this game and this book, if you’re looking specifically for a fully realized setting or consider that integral to your enjoyment of RPGs you’re probably going to be a bit disappointed.

The Basics

Cortex is at its core a ‘roll and keep’ dice mechanic. For any challenge the player assembles a dice pool of around three dice, rolls them, and keeps the highest two results. Depending on which of your character’s traits are relevant to the roll, you could be rolling d4s, d6s, d8s, d10s, or d12s, with d6 being average, larger dice being better, and d4 being much less good, especially considering the high probability of rolling a 1. All dice rolls are opposed rolls; the base dice pool that the GM rolls is two dice whose size vary depending on the difficulty of the task.

There are two other mechanics which depend on the die results. First is the Effect Die. Once a player chooses the two dice they wish to keep, they choose the largest remaining die to be an Effect Die. The Effect Die determines the impact of certain dice rolls, and is dependent on the size (rather than result) of the chosen die. This does mean that it might sometimes be advantageous to choose a lower absolute result (provided it still meets the threshold for success) if it produces a larger Effect Die. Second result-based mechanic is the Hitch. A Hitch occurs when a player rolls a 1 on one of their dice. A die showing a one cannot be chosen for results or for the Effect Die. While there are no direct consequences beyond that for rolling a one (only rolling all 1s is considered a critical failure and is called a Botch), the GM may choose to spend that 1 on the roll to create a Complication. Complications, and their positive counterparts Assets, represent circumstances or items that exist in a scene, much like Aspects in Fate. A GM can add the die value of a relevant Complication to the dice pool that opposes a character’s roll, while the player can do the opposite with a relevant Asset. When a character creates an Asset, they may use the Effect Die to determine its die size and therefore its impact on the scene. The other core mechanic of note is the Plot Point System. Each player starts play with a Plot Point, and when the GM activates a Complication from a player rolling a 1, they also give that player a Plot Point. Plot Points can be spent on activating abilities, counting more dice in rolls, and preventing a character from being Taken Out of a Conflict. As more options are defined, so too are more ways to earn and spend Plot Points.

That is, to say the least, a whirlwind tour around the Cortex mechanics. I haven’t gone deep, and haven’t even begun to get into how these dice pools are actually generated, save the basics of Assets and Complications. The issue with trying to explain many basic parts of Cortex Prime, like character creation, is that they are dependent on the options that are available and will look a bit different, at least at a summary level, depending on what you’re trying to play.

The Options

The Cortex Prime book is intended towards those who will be running games, and for that reason it’s laid out a bit like a menu. Although the first 45 pages are about the ‘core rules’, after the initial 8 page primer those core rules are already full of rules mods, reducing the linearity of the chapter. There are five mods for tests/contests, eight mods for Plot Points, and five mods for Assets and Complications. That’s eighteen mods for the ‘core rules’, and it goes without saying that the mods and options for character definition and scene management are even more expansive. 

Characters are defined by Traits, and the Traits that are chosen at character creation are divided into Prime Sets. These range from Attributes and Skills, which should be familiar to any gamer, to Affiliations, Powers, and Reputations, which assign die values to the size group your character works best in, chosen superhuman powers, and how well your character gets on in certain social circles, respectively. These choices are somewhat akin to choosing between Fate Core and Fate Accelerated, between Skills and Approaches, but there is significantly more granularity here. Beyond which Prime Sets you choose, the nature of the Prime Sets is incredibly customizable. If you were to use Attributes in your game, there’s a default list of three (Physical, Mental, Social), but you could easily expand that to D&D-standard six. While there’s a default skill list, you can change it as much as you want, and there’s guidance in the book on how to write skill lists with different intents as well as how to use a number of mods around skill specializations, rank structures, and role-defined skills.

All these Traits can be modified further, most notably with SFX. SFX detail specific pairs of costs and benefits which bring more granularity to traits; though they’re essential for certain Traits like Powers they can go with any Prime Set if that Prime Set is centrally important to defining characters in your game. While there are a number of costs and benefits from which SFX can be written, the central purpose of SFX in a game is to flesh out how Plot Points are spent and earned. The default SFX, Hinder, provides another way of earning plot points (the benefit) by allowing a character to bring the die for the associated trait down to a d4 (the cost). While the SFX attached to Attributes or Skills may be character-focused or situational, the SFX attached to Powers and Abilities are core to how they work; as such the book has more detailed lists of Powers, Abilities, and their attendant SFX in an appendix.

The options expand again when you get into running scenes and campaigns. While there doesn’t need to be a lot distinguishing combat from other contests, there are a number of mods encompassing initiative, hit points, Fate-like stress tracks, and anything else you can imagine to gamify your conflict experience. Similarly, the base advancement mechanic measures only sessions that have passed, but mods can get you Technoir-like stress-based advancement or Burning Wheel-like Belief mechanics if that’s the way you want to go.

One other interesting thing hidden in the various and sundry options is that it’s made clear that Cortex has been a game of evolution. Options from Cortex Classic are highlighted in certain places, likely because they’re a bit different from the way either Cortex Plus or Cortex Prime is structured. What these options are is enlightening: Cortex Classic was built around more classic hit point and initiative structures, and the game system as a whole moved away from these structures as it became clearer that they were neither complementary nor necessary. While there might be a hidden lesson in this, what we the readers benefit from is the choice to either go more modern or D&D-adjacent, losing nothing in the choice thanks to the game’s adaptability.

The Implications

So we have another generic RPG on the scene. It’s good, but why do I love it so much? The reason I’m such a fan of Cortex Prime, the reason I feel like it was written for me and how I run games, is that it’s written like a toolkit and with the intent of being used like a toolkit. All the core mechanics are there, all the optional rules are there, and they’re all clearly marked. Everything is explained and there are examples. There are either rules of thumb or meta-rules around how to build your chosen game. If you have a question about how to do something or why something came out the way it did, there’s likely an answer. I was at one point asked what Genesys could do to be a better generic RPG and the answer is, simply, this. Genesys didn’t come close to the utility in Cortex Prime until the Expanded Player’s Guide came out, and still it’s painfully clear that the intent of Genesys is just to make you use the published settings. With Cortex Prime, everything’s there to help you. It’s better technical guidance than Fate (which did get a lot better with supplements, the System Toolkits) and it’s a lot more concise than GURPS (which needed a supplement to explain all the supplements). There are drawbacks to this, especially if you’re just looking for a game to pick up. The organization of Cortex Prime is aimed at players for 8 pages and GMs for the rest, because the book is not a playable game out of the box…it’s even less of a playable game out of the box than Fate or GURPS. This is not a flaw, mind you…but it needs to be understood, because it should structure how GMs use the rules in the book to construct their games. The three settings in the book, in addition to being excellent worked examples of how to set up the game, are excellent examples of how the GM should present the game to their players. If you want to see what I mean, the Hammerheads setting is complete and playable right now, and is available to check out for free.

What makes Cortex Prime so good to me is that it is one of the few examples of a product which has learned from how people actually play and buy RPGs, especially setting-agnostic RPGs. The GM is the book’s audience, the GM wants to know how to run what they want and how to present it to their players. The GM may be the only person in the group who will buy the book. The players will read as little as possible to understand how to play the game, so it is more useful to equip the GM to write their own summary than it is to have an expansive player-facing section. Certain Agendas and Principles work as well for the game document as they do the GM. Structure any discussion of rules variants in such a way that you “Tell the Consequences and Ask”. Provide enough examples and discussion of how mechanics and variants work, but “Draw Maps, Leave Blanks” when it comes to the full breadth of possibility. And finally, “Be a Fan of the Characters” and make it clear that there’s no one right way to play with such a large palette. Cortex Prime may be the culmination of over 20 years of game development, but it’s clear that some big lessons have been picked up along the way.

Cortex Prime has been sent to distributors, and will be available at a game store near you soon. Cortex Prime is available to purchase online at

Header image by Natalia Bacetti, from the Cortex Prime gamebook.

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13 thoughts on “Cortex Prime Review”

  1. “One of the few products that has learned from how people play RPGs”
    “The GM is the book’s audience”

    To me it sounds like people finally figured out that the way that first edition D&D was laid out with a very short players handbook with nearly no mechanics and a huge DMs guide with everything needed to actually run the game was the way to go all along.

    Of course, it’s nice to see a game that’s actually got some production value following that approach instead of Gary’s rambling.


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