I sometimes play the Genestealer Cults faction in Warhammer 40,000. The new Genestealer Cults codex recently came out. I already own the digital index and the physical reference cards, but I purchased the new book for a few different reasons, and I've read it from cover to cover. This is my review of the Genestealer Cults codex for the 10th edition of Warhammer 40,000.
A codex for Warhammer 40,000 is a book containing lore, painting tips, and rules specific to the line of miniatures representing a faction in the game. If you take a minimalist view of games, a codex is mostly a lot of fluff around the specifications and numbers of a specific player token. And indeed, Games Workshop does provide just the specifications and numbers in what they call an index.
A codex isn't just about the game rules, it's about the game world itself. Why and how do the Genestealer Cults exist? What kind of weapons do its members use? Why might one cultist choose a specific weapon over another? What battle tactics do the Genestealer Cults use? Both the questions and the answers to them are entirely arbitrary and have no effect on the game. You can substitute chess pieces for the miniatures, use the index descriptions of abilities and the numbers assigned to attacks and saves, and play 40k without ever knowing what a genestealer was or why it had not just a single, but plural, cults.
A big reason for playing Warhammer 40,000 is its fictional setting. A codex isn't strictly necessary, but it's fun.
The Genestealer Cults codex for 10th edition Warhammer 40,000 contains 30 pages of lore, 12 pages of photos of painted Genestealer Cults, 10 pages of rules for Combat Patrol (the army-in-a-box version of 40k), 35 pages of rules, and 15 pages of rules for the Crusade campaign mode. Combine this with the 40k core rulebook, and you have all the paperwork you need for playing Genestealer Cults.
The lore section gives you a lot of background information about the cults, but most importantly it gives you inspiration on how to play the cults in a game of Warhammer. When you're able to roleplay (for lack of a better word) as the General of your army, a wargame is more fun than when you're just moving pieces around the board for purely strategic reasons. Sure, it's a wise move to flood that one objective with your troops. You're going to do it no matter what. And yet it's invigorating to announce that it's a ploy to infect innocent civilians so you win the narrative war even if you're defeated in game.
You don't need any of this to play, but it's a fun read and it gives you a lot to think about while you paint and play your army.
The showcase section of the book isn't objectively particularly useful. It might provide inspiration for how you choose to paint your own army, and I guess it shows you what an idealised game table might look like. Realistically, nobody is going to achieve what you see in the showcase. There are good painters and good miniature terrain modelers, but game tables just can't look like the book's photos, which are the product of professional lighting, a fog machine, digital retouching, and boundless resources.
I don't think the showcase section exists as something to literally aspire to, though. The showcase is the "movie" version of the game. It's got the sets that are larger (well, smaller) than life, the special effects, and the frame boundaries to crop out the rest of the room. The showcase photos are what we players see in our mind's eye as we engage with every step of the game, from making an army list to moving miniatures around the table and rolling a fistful of dice.
I basically skipped the showcase while reading through the book. But I know from experience that I'll find myself gazing at a photo some time in the future, inventing stories to go along with what I see, and planning out a way to play through that story with my own miniatures.
I have to confess that I didn't buy my Genestealer Cults army because I wanted to play Genestealer Cults. I bought into Genestealer Cults because the Combat Patrol box available at the time was a bargain. I got lots of miniatures in a single box, designed to play as a legal army in a small game of 40k, at the same price I would have paid for half as many miniatures of another faction. So I followed my wallet.
Bizarrely, that's not the Combat Patrol profiled in the Genestealer Cults codex. Just before the publication of this codex, a second Combat Patrol box was released with a lot more vehicles and far fewer infantry. I have to admit that I don't love vehicles in general, so I'm happy to have accidentally invested in the old Combat Patrol instead of the Claw of Ascension set. But that also means that the model profiles in this Combat Patrol section aren't useful to me.
However, the section itself still has some value. First of all, the army rules aren't specific to the any one Combat Patrol box. The Enhancements and Stratagems are general enough to be useful with the old Combat Patrol. I've even used Claw of Ascension in a fullscale game because, frankly, between all the special rules for individual models and the army and detachment, plus all the standard 40k rules, I usually end up forgetting to use half of what's available to me. If you're new to the game, fewer rules can be better, and the army rules for Combat Patrol are pretty minimal compared to most fullscale detachments.
The Combat Patrol section of the codex also provides some painting tips, which I appreciate. Painting tutorials these days are a dime a dozen thanks to the Internet, but I still enjoy seeing the basic steps explained in tidy photographs. It helps me remember that painting isn't as scary as it sometimes seems, when staring at 30+ gray plastic miniatures in need of paint.
The new Genestealer Cults codex for 10th edition of Warhammer 40,000 provides rules that aren't included in the core rulebook especially for your Genestealer Cults army. From a gaming perspective, that's one of the three main selling points of this volume.
First of all, you get an Army Rule that applies to your army just because you're playing Genestealer Cults. Those rules aren't in the 40k core rulebook, because they're specific to Genestealer Cults. This is one of the things that gives your army choice meaning.
Secondly, you also get to choose an army variant (called a "Detachment") containing Stratagems (which you can "buy" during the game with Command Points) and other special rules. This helps you optimise how you've built your army. For instance, if you've chosen to include some infected Astra Militarum forces along with your Genestealer Cult army, then there are special rules that give your Brood Brothers extra power. Those rules would be meaningless to an army without any Astra Militarum models, though, so you'd choose a different Detachment for armies built around, say, Aberrants or Purestrain Genestealers.
The subsection containing Detachments is deceptively small. It's just 6 or 7 pages, but it's probably 80% of the value of the codex. With these Detachments, you can change the way your army plays, either in the interest of strategy or just for the fun of it. I've had a blast running my army as an ambushing infestation of Tyranid harbingers, but also as a force of fanatical religious crusaders. Same models, totally different style of play.
The third reason the codex exists is for the datasheets. This section provides specifications for each legal model type, and the numbers you need to beat on the dice for each model to succeed at whatever it's trying to do. This section of the book is literally the game. With this paperwork, you could buy a bag of classic green plastic soldiers and substitute them in for the miniatures you see here, or you could play the entire game in a spreadsheet. The datasheets have the numbers that determine how far a specific model can move, what value it needs to hit its target, the strength of its weaponry, the target number to save against attacks, and so on.
The typical datasheet in this book has extra information, thankfully, like what each possible weapon actually looks like. Genestealer Cults has a dizzying array of weaponry, from stolen Astra Militarum guns to weaponised mining tools, and it can be baffling to tell them all apart. This codex helps with that. On page 100, there's a 2-page spread called Weapons of the Genestealer Cults and it makes a truly noble attempt to name each weapon you're likely to see as an option in any given box. It doesn't entirely succeed (which is weird, because the company that produced this book is essentially the same that produces the models). Instead of just looking at literally all the options they provide with each model (which they surely have on file), the authors of the book take a sampling of weapons, I think from the 2024 Combat Patrol box. It covers a lot, but I've definitely got weapons on my miniatures from the 2023 Combat Patrol box that are not named in this spread. This is one of the most frustrating parts of 40k in general. While building, it's hard to know what weapons your models are "supposed" to have, or which weapon is what in the first place. After that, you're meant to keep all those weapons straight on the game table, and map them back to text in datasheets. I guess I'm slowly getting better at recognising the weapons, but mostly I just make my best guess during a game, with the secret hope that a very experienced player will tell me what weapons I've actually brought to the table.
The rest of the book covers Crusade rules, which allows you to reward your army with experience points and special powers based on the battles they fight. Instead of playing a single game of 40k with your army, you track your army over the course of several battles. I haven't used the Crusade rules yet because the codex is so new, but I'm looking forward to tracking my army for a full campaign.
This is a fun book. It's by no means essential. If you downloaded the index from Games Workshop when 10th edition first came out, then you can play Genestealer Cults using those stats. If you bought the data cards from Games Workshop, you can just use those (they include the Army Rule and a generic Detachment option). But if you get the codex, you also get lots of fun lore, beautiful pictures, and lots of fun rules to try out. Appropriately, it's an army book that includes everything you could want for your army. I'm happy I bought it, and I'm having a blast using it in my games.
Traitor guardsmen photo by Seth Kenlon.