- "I am a Child of the Omnissiah, cultist of the Machine God. The rites of manifold applications, the liturgies of ignition and the songs of Engine-seeing are mine own to know. I speak to the spirits of ancient tech-machines, from the warrior heart of a battle tank to the secret wisdom of the cogitator."
- — Vox Servitor Theta, on behalf of Cult Mechanicus Adept Manuel.
A Tech-Priest is an Adept of the Adeptus Mechanicus of the Imperium of Man who is generally responsible for maintaining all of the advanced technology of the Imperium, enlarging the Imperium's stocks of technical knowledge and conducting what little new scientific research occurs within the Imperium since the end of the Horus Heresy. Tech-priests are members of the Cult Mechanicus, the Cult of the Machine, a priesthood which forms an ecclesiastical hierarchy for the Cult Mechanicus of technicians, scientists, and religious leaders who believe that knowledge represents the only true divinity in the universe. The Tech-priests provide the rest of the Imperium with its technicians, scientists and engineers. Though their bodies often incorporate many inorganic components as bionic replacements, Tech-priests are fully human, unlike the cybernetic Servitors created by the Adeptus Mechanicus that carry out most of the heavy labour for all of the Imperium's myriad organisations and enterprises.
The Priesthood of Mars
The Fabricator-General of Mars is the leader of the entire Adeptus Mechanicus, and also serves in the position of the Magos Mechanicus, the chief priest of the Cult Mechanicus, the religious hierarchy that coexists alongside the Mechanicus' more secular function for the Imperium. The Fabricator General of Mars administers not only the Adeptus Mechanicus but also governs the planet of Mars itself as the recognised Imperial Planetary Governor. As befits his position, the Fabricator-General of Mars has a permanent seat on the council that runs the Imperium, known as the Senatorum Imperialis of the High Lords of Terra. Rulers of individual Forge Worlds are referred to as Fabricator Generals as well, but only the Fabricator General of Mars holds a seat among the High Lords of Terra.
The Fabricator Locum is the second highest-ranking individual on the planet of Mars and other Forge Worlds. The Fabricator Locum assists the Fabricator General with the governance of Mars, including the meeting of production quotas and ensuring the correct devotions to the Machine God are observed at all times. The most notable Fabricator Locum was named Kane. He sided with the Emperor of Mankind during the Horus Heresy and thus maintained at least some crucial Mechanicus support for the Loyalists.
A Magos is a master of a technological or scientific discipline, having devoted many years of service to the Omnissiah in that area of study. There are many specialist divisions within the Adeptus Mechanicus known as Divisiones. Magi from these are given a rank containing the specialisation of their Divisio, such as Magos Alchemys, Magos Biologis, Magos Technicus, Magos Logis, Magos Xenologis, Magos Lexmechanicus, Magos Orbologis, Magos Cybernetica, Magos Xenobiologis, Magos Astrologicus, Magos Digitalis, Magos Fabricator, Magos Genetus, Magos Physic, and possibly many more. There are two higher ranks within the Divisiones that are variations of the Magos, including Archmagos and Archmagos Veneratus. It is not known what the specific connotations of these titles are, though presumably they are indicative of greater seniority and experience.
- Magos Explorator - Obsessed with the Cult Mechanicus' Quest for Knowledge, the senior Tech-priests who serve as a Magos Explorator search high and low across the galaxy for lost Standard Template Construct (STC) databases and ancient human scientific and technical knowledge lost during the Age of Strife. A breed apart from regular Tech-priests, any Explorator or member of his team will willingly walk into forgotten catacombs, even at the risk of death, for mere snippets of long-forgotten knowledge from the Dark Age of Technology. Many Magos Explorator command the Explorator fleets that continue to push outward the frontiers of the Imperium or even serve alongside Rogue Traders.
- Magos Errant - Something of a jack of all trades, a Magos Errant studies several scientific and engineering disciplines, including chemistry, genetics, metallurgy and more. They are then attached to Rogue Trader fleets and other similar Imperial expeditions by treaty between the Adeptus Mechanicus and the individual Rogue Trader houses or the Imperium itself if the expedition is sponsored by the Adeptus Administratum. In return for the Adeptus Mechanicus' expertise in technical maintenance and science, the Magos Errant is allowed to study interesting sites the expedition comes near, transport sensitive materials and generally make use of the expedition's resources for the greater good of the Machine God.
A Logis is a Tech-priest skilled in mathematics and data analysis who serves in the role of a logistician, data analyst, or statistician. His purpose is to predict future large-scale demographic, sociological or demographic trends and make forecasts about the required expenditure or other strategic needs. They are regarded as prophetic figures by the Cult Mechanicus.
A Genetor is the name derived from High Gothic that is given to a high-ranking Tech-priest specializing in the genetic sciences and biological engineering. Sometimes referred to as Magos Biologis, Genetors number alongside the Logis, Artisan and Magos ranks of the Adeptus Mechanicus as its ruling Priesthood, possessing access to knowledge and resources far beyond that of the lesser Engineseers and Lexmechanics. A Genetor's field of study makes him distinct from the majority of Tech-priests as their professional obsession with organic life often makes them seem strange to their more mechanically-inclined brethren. Their interest in the organic is not merely limited to their own forms, or even to that of humans. The study of alien genetics, to understand how they function so as to slay them better in the name of the Emperor, is a common field of study for Genetors, particularly the sub-sect collectively known as the Xenobiologists. Such knowledge is dangerous, and many Genetors have been condemned as Heretics for claiming the superiority of a particular xenos’ biology to that of Mankind. Genetors are very common in the Adeptus Mechanicus, and often accompany Imperial forces on exploration missions to new worlds. They are also the members of the Adeptus Mechanicus responsible for testing the 5% tithe of gene-seed provided to the Mechanicum by every existing Chapter of the Adeptus Astartes for signs of mutation or corruption by Chaos. The Genetors also use these tithes of genetic material when the Imperium requires the Founding of new Space Marine Chapters every few centuries.
A Xenobiologist is a sub-sect of the Genetors who study alien genetics to gain a better understanding in how their physiologies function so as to slay them better. Such knowledge is dangerous, and many Genetors have been condemned as Heretics for claiming the superiority of a particular alien species' biology to the sacred form of Mankind. Regardless, the presence of a Genetor, particularly a Xenobiologist, is seen as an asset by Explorator Fleets and Rogue Traders alike, as their knowledge of human and inhuman forms allows them to discern the nature of a newly-encountered xenos or indigenous species, or categorise a new strain of Abhuman found on a far-flung world.
Artisans, sometimes called Constructors, are the Tech-priests who design and build new devices, edifices, spacecraft, weapons, technology and other Imperial military hardware. They essentially serve as the Mechanicus' all-purpose Corps of Engineers and can be found pursuing construction projects across the Imperium. They also control the vast corps of Servitors employed by the Adeptus Mechanicus for all of their labour needs.
Electro-priests are fanatical warriors for the Cult Mechanicus, and are tasked with using their cybernetic abilities to support other Tech-priest warriors, Combat Servitors and the Mechanicus' dedicated combat troops, the cybernetic Skitarii or Tech-Guard, in battle. Their dermal layers are implanted by the Magos Cybernetica with metallic Electoo circuits throughout their bodies. These circuits are designed to interlink with the Electro-priests' neural cortex, which allows them to generate a tremendous amount of bio-electrical energy which they can release in powerful and devastating blasts. When Electro-priests enter battle they chant litanies to the Omnissiah of the Cult of the Machine, whipping themselves into a fanatical state of hatred towards the Mechanicum's enemies and building up the electrical energy that they will release in an orgy of destruction on the battlefield.
Enginseers are perhaps the most common of the Tech-priests of the Adeptus Mechanicus. They view themselves as engineer-mystics dedicated to the Omnissiah, and each Enginseer possesses a wealth of knowledge on how to maintain and repair mechanical and electronic technology. Unlike most of the Priesthood of the Adeptus Mechanicus, Enginseers can be found serving in almost every Imperial institution (other than the Adeptus Astartes, where the same role is played by the Techmarines), and are often assigned to regiments of the Imperial Guard or other parts of the Adeptus Terra. Enginseers are highly-trained members of the Cult Mechanicus and are dedicated to the maintenance of Imperial technology. Through many years of study, they have gained the knowledge of the arcane rituals and processes that form the body of Imperial technical lore as practiced by the Mechanicus, as well as a more secular understanding of the more practical disciplines of mechanical and electrical engineering. Enginseers serve across the galaxy with the Imperial military, often in harm's way, as they will be called on to make repairs on the battlefield as well as in the workshop. They are a common sight during engagements where the Imperial Guard's forces have engaged large numbers of armoured vehicles, and are often accompanied by a contingent of Servitors for either assistance with the work or defence. Although most Imperial Guardsmen revere their vehicles' Machine Spirits enough not to irritate an Enginseer by committing blasphemy in the form of "customisation," the modification of vehicles to fulfill a certain need is inevitable, much to the horror of any Enginseers' religious principles. Enginseer contingents are also included in the mighty Titan Legions of the Adeptus Mechanicus' Collegia Titanica and the crews of the massive warships of the Imperial Navy, allowing them to perform emergency repairs in the heat of battle. Despite the respect they usually command among the units they are seconded to, Enginseers are not held in high regard among the Cult Mechanicus itself as their skills seldom contribute to the divine Quest for Knowledge which is the chief religious duty of any servant of the Machine Cult. As a result of the overwhelmingly practical rather than theoretical bent of their knowledge, Enginseers are often perceived as no more than a necessary but lowly underclass in the workings of the Cult. Enginseers almost always make use of the cybernetic enhancements that are common among tech-priests, in this case bionic arm augmentations that appear to be very similar to serpentine tentacles known as Mechadendrites. These augmetic limbs are used to help the Enginseer during repair operations, to carry out tasks requiring strength beyond the human norm and in many instances for self-defence.
A Rune-Priest is a Tech-priest who is responsible for performing the rituals required by the Cult Mechanicus' doctrines for the awakening of Machine Spirits. These rituals involve the scribing of runes and the chanting of Cult Mechanicus liturgies over the devices to be so awakened. Rune-priests are often experts after years of studying perhaps the most arcane branch of science explored by the Adeptus Mechanicus: intuitive mechanics, better known as speculation and improvisation. Rune-priests are famous (or infamous by the standards of the more logic-minded Tech-priests) for their unorthodox solutions when strict logic and standard procedures prove inadequate to the task at hand.
Transmechanics are those Tech-priests who specialize in the repair, operation and maintenance of the Imperium's various forms of communications technology. They are often assigned to serve in other organisations of the Imperium like the Imperial Navy.
The purpose of the Tech-priests called Lexmechanics, who are also known as Calculus Logi, is to compile data so that it can be entered into a central Cogitator (computer) repository. Lexmechanics are the librarians and scribes of the Mechanicus. They work with computer-like speed and accuracy, assembling battle reports, economic statistics, planetary reports, and other masses of necessary if mundane data required to keep the massive bureaucracy of the Imperium functioning from day to day. They are used throughout all the divisions of the great galaxy-spanning bureaucracy that is the Adeptus Terra, but are most concentrated in the Adeptus Administratum.
- Codex Imperialis (1st Edition), by Rick Priestley, pp. 41-46
- Dark Heresy: The Lathe Worlds (RPG)
- Fanatic Magazine 5
- Realm of Chaos: The Lost and the Damned, pg. 169
- Rogue Trader: Hostile Acquisition (RPG), pp. 85-88
- Rogue Trader: Into the Storm (RPG), pp. 82-83
- The Artwork of Clint Langley, pp. 30-31
- Warhammer 40,000: Rulebook (6th Edition)
- Warhammer 40,000: Rulebook (5th Edition), pp. 106, 110-111
- Warhammer 40,000: Rulebook (4th Edition), pg. 121
- White Dwarf 308 (US), "Priests of Mars", pg. 84
- White Dwarf 191 (US), "Ordinatus: Imperium - The Adeptus Mechanicus", pp. 49-53
- White Dwarf 178 (US), "The Titan Legions: History, The Adeptus Mechanicus - The Birth of the Cult Mechanicus", pp. 45-52
- White Dwarf 140 (US), "Space Fleet: Adeptus Mechanicus", pp. 46-75
- Xenology (Background Book)
- Mechanicum (Novel) by Graham McNeill
- Dark Adeptus (Novel) by Ben Counter
- Dark Apostle (Novel) by Anthony Reynolds
- Helsreach (Novel) by Aaron Dembski-Bowden
- Iron Hands (Novel) by Jonathan Green, pg. 122
- Titan (Novel) by Dan Abnett, Anthony Williams and Andy Lanning
- Priests of Mars (Novel) by Graham McNeill