Knowledge is a funny thing, especially in the 41st century. Much has been lost completely, other bits are deemed too dangerous to know... and a lot is kept firmly in the grip of the Adeptus Mechanicus, who regard technology in a sacred light as they worship the God-Emperor as the Omnissiah, the Perfect Sum of All Knowledge. Not for nothing are they called the Cult of the Machine God. Within the Calixis Sector, they are concentrated on the Lathe Worlds, and this book serves to convey a wealth of information about both the Adeptus Mechanicus and the three worlds on which they congregate.

Chapter 1: The Cult Mechanicus starts off by presenting their origins and history, with special emphasis on their role within the Calixis Sector. Going back to the earliest times it seems that Mars, in the Earth system, saw their very beginning and that it was here they established their first forges - for they control all production facilities for virtually all technology especially that of a warlike nature, and claim ownership of every discovery, be it new research or the finding of long-lost technological items from the distant past. It is said that they were established on Mars even before the God-Emperor came to prominence on Earth and were amongst the first to recognise his importance, if not divinity. Their hierarchy and organisation are covered before a discussion of their quest for knowledge and and their holdings in the Calixis Sector. Ritual is integral to everything that they do, and quite a good overview is given of that - as it underpins virtually all use of technology this is well worth understanding. Like any organisation, there are factions and sects amongst them, and some heresy as well.

Next, Chapter 2: Servants of the Omnissiah provides all the game mechanics necessary to creat characters (and, of course, NPCs) who are members of the Adeptus Mechanicus - a goodly array of new options, backgrounds, career ranks and more. This will enable you to model adherents of the different factions and bring much more depth to Adeptus Mechanicus characters wherever they are encountered in your game.

Then Chapter 3: Dominions of the Lathes looks at the Lathes system, reviewing the planets, artificial stations and indeed the vast array of holdings that the Adeptus Mechanicus has here. There's a lot of information in this section, and it will enable this area of space to come to life whenever the party happens to visit. There are even more sects and factions specific to the Lathes system for those who enjoy intrigue, and the whole chapter is liberally supplied with adventure seeds... not to mention it spawns quite a few just as you read through the information herein!

Finally Chapter 4: The Light of Reason is an adventure that will send Acolytes to investigate psychic disturbances in the Lathe System... who is dabbling in what dangerous areas and can they be stopped in time? They will have to pick their way through faction politics, explore the darker corners of the Lathes system, and perhaps may come to understand why the Adeptus Mechanicus thinks the way it does. There's plenty of support for the GM, from environmental hazards to atmospheric descriptions, and whilst linear in concept the adventure is constructed in such a way that the party will feel like they can find their own way through it to the ultimate climax.

With technology and the religious approach to it being so embedded in the Imperium, this is a useful book to have for general background: if you want the Adeptus Mechanicus to feature large in your adventures, you'll need it.

In many ways, ‘The Lathe Worlds’ is an essential book for all of the 40K-based RPGs, not just Dark Heresy. The Adeptus Mechanicus are well-deserving of their own book, given that there are a number of cultural, perceptual and even theological differences between those adherents of the Machine Cult and the rest of the Imperium of Man.

The developers for this product have done an excellent job in creating a resource which will see a lot of use at any table, with a clarity of writing, and clean layout which to which I have become accustomed when dealing with materials from FFG. Divided into four sections, the book covers in detail:

The history of the Adeptus Mechanicus, their hierarchy and how they are viewed by the general populace of the Imperium. It provides some interesting social norms about the role of machines and their appointed guardians and how this plays out in day-to-day life; which is invaluable for the GM, but also provides inspiration for players. It concludes with a section on tech-heresy, which firmly roots this book into the Inquisitorial ideology and provides a wealth of ideas for adventure design. The second chapter is, by necessity, the rules-heavy section. IT deals with alternate career paths, skills and talents and the armoury (providing a host of new toys for your campaign). Overall, the quality of the Career Paths is high, and wargear section doesn’t contribute to an ‘arms race’ mentality which is rife in the 40K tabletop game, so this is a nice divergence for the tabletop RPG to take. The penultimate chapter deals with the establishment of the Lathe Worlds, the power groups and planets. The planets in particular are given a lot of attention, and fleshed out quite well. The challenge in approaching a subject like mapping an entire system of planets is to balance the amount of detail. FFG handles this very well, providing enough information to spark the imagination and give a unique feel for each locale, but not so much that the reader becomes bored with the level of detail.
Lastly is ‘The Light of Reason’ an adventure which utilises the information and ideology of the book very well. It shows, in practical terms, how tech-heresy and the Doctrines of the Mechanicus are interpreted and what occurs when these teachings are blatantly ignored. Obviously, to get the best out of this adventure (and the book as a whole) you’ll need a Tech Priest in your party, but I can see this book of use to those who have yet to succumb to the lure of the Omnissiah too.

Overall, it is a fine work, capped off by a module which is thoughtfully written and offers a great experience at the table. I would have liked to see an Index included in this book, especially given the new content, but the information is generally well-laid-out, so FFG can be excused for this. The artwork continues to impress, with enough smatterings of established artists to aesthetically link the book back to the wargaming supplements. Whilst Mechanicus characters appear in a few Black Library books (such as the Shira Calpurnia novels) and audio dramas (most notably ‘Red and Black’), they do require a book like this to give them more defined substance. Given that Games Workshop is releasing Chaos equivalents of the Tech Marine for the new Codex, there is scope for this book to be used to develop adversaries as well.

I can see this becoming part of my ‘essentials’ for Dark Heresy and it is proof that sometimes the inner workings of the Imperium are far more strange and compelling than that which lurks on its edges.