When Games Workshop dropped the third edition of Warhammer: The Horus Heresy in 2025, they brought with them a doorstop of a book that weighs more than a newborn baby. At 352 pages, Liber Hereticus isn’t just hefty—it’s the kind of tome that makes you understand why the Word Bearers were so obsessed with forbidden knowledge.
What You’re Actually Getting
Let’s cut through the marketing speak. This book consolidates what used to require multiple volumes into one comprehensive resource. You’re getting complete rules for all nine Traitor Legions—Emperor’s Children, Iron Warriors, Night Lords, World Eaters, Death Guard, Thousand Sons, Sons of Horus, Word Bearers, and Alpha Legion. The first 140 pages mirror what’s in Liber Astartes, covering the core Space Marine army list. The remaining pages dive into legion-specific rules, units, and the Primarchs themselves.
Here’s what matters: each Legion has access to Rites of War, unique detachments, weapons, characters, and units to bring legion-specific flavor. This isn’t just cosmetic variety—we’re talking fundamentally different playstyles.
The Good Stuff
Organization That Actually Makes Sense
After years of hunting through multiple Black Books for a single unit profile, the consolidation is a godsend. Each of the Liber volumes has the full list of Universal Special Rules, Wargear and Weapons in the back, which means you’re not constantly cross-referencing during games. This might seem basic, but it’s a massive quality-of-life improvement.
Legion Diversity That Matters
The Emperor’s Children exemplify how Games Workshop has differentiated the legions. They actually exist as two distinct armies within one legion entry—the standard Third Legion and the corrupted Hereticus version. The base legion gets +1 Initiative on the charge, while Hereticus Emperor’s Children keep the Stupefied mechanic from last edition, but it is massively increased in usefulness. Units can become Stupefied during shooting attacks, gaining bonuses to Strength and Feel No Pain but losing the ability to react. It’s high-risk, high-reward gameplay that feels thematically appropriate for sensation-seeking degenerates.
The Sons of Horus bring something different entirely. Their faction trait, Merciless Fighters, gives non-vehicle opponents -1 strength on their attacks in any turn where charging or being charged occurs. This seems subtle until you realize it’s keeping your terminators alive against power fists and making your own melee attacks devastatingly effective.
The Primarchs Are Actually Primarchs
Each Traitor Primarch gets a full profile, and they’re appropriately terrifying. Angron’s ability to fight multiple challenges is really powerful and interesting, allowing him to pick his way through various Command and Challenger models in a unit accumulating Combat Resolution Points. This isn’t just stat-padding—it creates tactical decisions about where to commit your demigod.
The Reality Check
Weight and Portability
At eight pounds for both Libers combined, they feel like they’re more designed for list building at home than hauling them to games. You’ll want to make cheat sheets or use digital resources for actual gameplay. This isn’t a dealbreaker, but it’s worth knowing before you throw your back out carrying your army and rulebooks to game night.
Legacy Unit Limbo
Some units got cut from the physical book and relegated to PDF “Legacy” rules. The logic is that only units with current models made the cut, which makes business sense but fragments the experience. Players noted they can buy Tartaros Terminators with power fists in the box, yet the rules don’t support this option. These gaps require tracking down additional PDFs, which somewhat undermines the “everything in one place” promise.
The Learning Curve Is Real
Third edition fundamentally changed how Horus Heresy works. You’ve got three mental stats alongside Leadership now, and sergeants need a special rule to test Leadership for their unit. The reaction system expanded from one per phase to a pool-based system with costs. If you’re coming from second edition, expect to relearn significant portions of the game.
Who Should Buy This
If you’re building a Traitor Legion army, this book is mandatory—not in a “nice to have” way, but in a “you literally cannot play without it” way. At around $60, it’s not cheap, but consider that it replaces what used to be multiple books.
For veterans of previous editions, the consolidation and improved organization justify the purchase, even if you’re wincing at relearning familiar legions. The rules updates generally improve gameplay depth, even if they require adjustment.
For newcomers intrigued by the grimdark civil war setting, Liber Hereticus offers nine distinct armies in one book. That’s genuine value if you’re still figuring out which legion calls to you. Just know you’ll also need the core Age of Darkness Rulebook to actually play.
The Verdict
Liber Hereticus succeeds at what it sets out to do: provide comprehensive, organized rules for the Traitor Legions in a single volume. The legion-specific mechanics create meaningful tactical differences, and the production quality matches the premium price point. Yes, it’s heavy. Yes, you’ll need to reference PDFs for some units. Yes, the learning curve is steep.
But here’s what matters—when you field your World Eaters in a berserker rage or coordinate your Alpha Legion’s infiltration tactics, the rules support those thematic moments while maintaining competitive balance. That’s harder than it sounds.
Rating: 4 out of 5 power claws
The Liber Hereticus delivers what Traitor players need, even if the package requires some muscle to transport. For the inevitable heresy on your tabletop, this tome is worth the weight.