A Magos is the big cheese, the mega IT nerds, the technophile supreme of the Adeptus Mechanicus (save for the Fabricator General of Mars of course). Magos, as expected, are masters of a technological or scientific discipline, having devoted many years of service and furiously masturbating to the Omnissiah in that area of study. As you would expect from such a high rank from the Mechanicus, a Magos is mostly at the bare minimum, 80% machine; a Magos has replaced so much biological body parts for mechanical ones that they are more machine than man.
Unlike say...a Chapter Master or a Canoness, there are many different types of Magos each specializing in a particular field within the Cult Mechanicus. Such specialist divisions within the Adeptus Mechanicus are 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, etc.
The best thing about them is that unlike the rest of the priesthood, a Magos is privy to do things that under normal circumstances would be even considered borderline Tech-Heresy (such as inventing new technology, constructing new vehicles and creating new STC from existing ones, or even doing actual research) without anyone shooting them for it due to the fact that they actually have the brains and imagination to not create something that will end in a horrible (mostly) way. Though it is very limited due to many superstitions and out of fear that they'd go too far over the line.
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.
The rank structure of a Magos is highly complex with too many sub divisions to make for a clear understanding. Here are those official ranks that is documented by permission of a member of the Cult Mechanicus.
- Prime Hermeticon - Highest rank
- Lord Dogma
- Mechae Moribundus
- Invictus Acquisitor
- Data-Predator - Lowest rank
To be promoted to Magos is not routine. Unlike purely gerontocratic systems like those found in the Imperial peerage and some Space Marine Chapters, one must be specifically selected to be a Magos by a committee of those who hold the rank already. This ensures that most Magi will actually do something with their job instead of just filling it until they die, most of the time.
Types of Magos
As you know, there are lots and lots of different divisions of a Magos. Here are the ones more commonly known and seen in the wider Imperium.
- Magos Explorator: AKA the most adventurous type. Think of them like Indiana Jones but with more cybernatic implants. These Magos are the ones you see searching for STC's and Archeo-tech. 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. As you can imagine, these guys are a walking disaster waiting to happen and will be the ones most likely to poke a sleeping Necron Tomb World to see if it gives off a spark only for Ciaphas Cain *HERO OF THE IMPERIUM!* to come in and save the day. Many Magos Explorator command the Explorator fleets that continue to push outward the frontiers of the Imperium to boldly go where no one has gone before or even serve alongside Rogue Traders.
- Magos Errant: The 'Jack of All Trades' type of Magos. 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. They are one of the most flexible types of Magos and while not a master in any of the scientific areas that other Magos specializes in, they at least provide ample help that will the specialized Magi divisions cannot match.
- Magos Juris: These guys are one of the rarer types of Magos. The reason they are relatively rare is that they choose to devote their minds to the study of the Machine God's will rather than the knowledge it embodies, removing themselves from the Quest for Knowledge in order to preserve it from the abuses of the heathen masses of Mankind. A member of the Mechanicus that removes itself from the rediscovery of lost technology is unheard of, hence their relative rarity. Think of them as cyborg philosophers akin to Socrates or Confucius. Because of their closer connection to the Machine God, Magos Juris are much more zealous and dogmatic in their ideology. Therefore these Magos hunt down any who would employ unsanctioned technology or, even worse, operate technology without the blessing and oversight of the Adeptus Mechanicus. Magos Juris will go so far as to even take Mechanicus voidships into the depths of the Koronus Expanse to hunt down their foes. Emprah help your ass if you commit tech-heresy or try to smuggle technology from the Mechanicus. Don't fuck with these guys.
- Magos Dominus: Also known as Tech Priest Dominus, these are the guys in command of the Legio Cybernetica, Electro Priests, and Servitors. Magos Dominus control the basic battle congregations of non-Skitarii and Titan Mechanicum forces. They are often masters of much of what remains of the vast and potent secrets of the Dark Age of Technology. They are the ones you typically see in the battlefield as their expertise on the majority of the Mechanicum army force these guys to get in the midst of battle. They don't need to worry of course, since the amount of in built weaponry these guys harbor would make everyone think twice in trying to attack them.
- Magos Reductor: Magos Reductors are a type of militant Magos by the Ordo Reductor of the Adeptus Mechanicus. The supreme officers of the Ordo, these Tech-Priests were a breed apart from their politicking kin on Forge Worlds. A Magos Reductor is a master of siegecraft, extermination, and warfare rather than creation and the acquisition of techno-arcane lore. They are renowned for their cold and ruthless demeanor even by Mechanicum standards. Imagine each and everyone of them as a mini-Perturabo, that should give you a clue on what they are like in both the battlefield and in mannerisms. They are often considered as the heavy weights among the Magos due to their specialty in sieges and charges and are often decked with the most heaviest weapons possible in order to crack open some defensive walls.
- Magos Prime: These are the big wigs of the Magos Divisions. Magos Prime are another type of Adeptus Mechanicus Magos armed and trained for war with the finest armaments and defenses. They are chosen from their peers to lead in battle and in most cases are heavily augmented with weaponry and armor. Some Magos Prime may even resemble Space Marine Dreadnoughts. The Magos Prime itself is split into several types, from the mighty Archimandrites who command entire Forge Worlds when they go to war and are rulers in their own right to the pathetic Lachrimallus who are nothing more than glorified slave drivers.
- Magos Biologis: Probably one of the more boring types of techpriest. These are your biologists, experts on how both the body of man and the alien works. If Inquisitor Martyr is to be believed, they actually have the expertise to diagnose the cures for serious injuries and diseases, and in some cases even cure them. Give them some samples from a Tyranid hive and they can usually cook up something nasty to make it and all its spawn die horribly. They're also responsible for examining and ensuring that all Gene-Seeds are clean, making them vital to the founding and survival of an Astartes chapter. In short, they are akin to modern biologists/doctors, but with more species to study. Other Magi regard the Biologi with a bit of suspicion as their philosophy about humanity and the Omnissia diverges somewhat; most Biologi are "apexists", which is basically an even-more-grimdark version of Darwinism. While this schism is not as radical as the split between puritan and radical inquisitors, a Magos Biologi would nod approvingly at the antics of an Istvaanian.
Being the big cheese of the Mechanicum forces, a Magos can be equipped with pretty much anything if he feels like it. However these are the tools they most likely use in most expeditions.
This includes Ryza Pattern Plasma Pistols, Sollex Pattern Omnissian Axe, Hellpistols, Chainsword, Mechadendrites, Power Axes, Melta bombs, Rad Grenades, Phosphex Bombs, Breacher Charges, Archaeotech Pistols, Photon Gauntlets, Maxim Bolters, Meltaguns, Graviton Guns, Photon Thrusters, Phased Plasma-Fusils, Irrad-Cleansers, Volkite Weapons and many, many more. If it can be carried to battle without having to be mounted on big walkers or super heavy tanks, the most fuckingest of dakka and choppa are available to them.