Skitarii

The Skitarii, also known as the Tech-Guard, are the cybernetic military forces of the Adeptus Mechanicus of the Imperium of Man. They are used to defend Mechanicus Forge Worlds, manufacturing installations elsewhere in the Imperium and often accompany high-ranking Tech-priests and Magi as their bodyguards. Skitarii also serve as the armed forces that defend the Mechanicus' Explorator vessels that explore the galactic frontier, and also safeguard Titans on campaign from boarding actions and prevent hostile forces from reaching the war engine's dead zone, where its main weapon batteries are useless. A number of Titan Legions maintain their own Skitarii detachments for this purpose, and if they do not, their Mechanicus masters will provide ample forces to protect the God Machines. The term "Skitarii" is formally applied by the Tech-priests of the Mechanicus to all of the military forces under their command, including infantry and armoured vehicles, save for the Titan Legions and the Knights. However, the term colloquially has often referred solely to the Adeptus Mechanicus' cybernetic infantrymen.

Origins
]] Skitarii are born into the service of the Mechanicus either as natural-born human Menials of the Mechanicus who are cybernetically-enhanced specifically to serve as Skitarii or they are genetically-engineered clones or vat-born humans who are cybernetically enhanced from the moment of their accelerated "birth", much like certain types of Servitors, though unlike those cybernetic Menials most vat-born Skitarii are allowed to retain at least a modicum of their higher brain functions so that they can follow the more complex orders often given on the battlefield. Skitarii train with their integrated cybernetic weapon until they are of the appropriate age to be sent into a war zone. To guarantee their undying loyalty to the Adepts of Mars, all Skitarii undergo various forms of psychosurgery. Some have their minds wiped of both emotion and personality and implant mental directives designed to ensure that they follow the orders of their commanding Tech-priest or Magos without question, even to the point of being remotely controlled. Other Skitarii are allowed to retain a certain degree of personality, although their defining traits will always be belligerence and the desire to fight. Skitarii undergo genic programmes that develop strenght and agression, and are augmented to further these traits. During battles the Tech-guard go into a hormone-induced rage, and likely become addicted to the adrenal high that close combat delivers. Despite this, however, the Skitarii, particularly the commanders, are neurally modified so that the analytical parts of their brains remain a bastion of calm amidst a storm of wrath, allowing them to quickly evaluate the tactical and strategic situation, and act accordingly. Along with their ability understand binaric code which can be nearly instantenously sent, received and understood by their augmented cerebral cortices, this allows them to operate with a very remarkable degree of cooperation and reflexes -- something all the more stunning to be seen in a seemingly ragtag horde. Like all of the Adeptus Mechanicus the Skitarii are expert at multitasking, and a Tech-Guard officer can, for example, at the same time effortlesly engage in viscious close combat, direct the forces under his command, oversee the tactical situation of the battle and provide coordinates for Balisteria artillery detachments. As mentioned above, however, not all of the Tech-guard are so skilled, and some are merely remotely controlled or preprogrammed weapon platforms, though these are mostly used to guard static locations. The level of cybernetic enhancement may vary between each Skitarii. Some may only have a few genetic and bionic enhancements, while others may have replaced whole organ systems with technology.

Wargear
Skitarii regiments that go to war alongside the Mechanicus' Titans are equipped with a variety of esoteric weapons of war. Part man and part machine, the brains of most Skitarii have been cybernetically hard-linked to their personal weapons for increased performance during combat. The heaviest ordnance is at times mounted on tracked, gene-bulked combat Servitors, which can effortlessly carry such weapons and keep up with the rest of the Tech-Guard's advance. Most of the Skitarii are also equipped with close combat weapons, some utilising Mechadendrites for the advantage that an additional limb confers, and some are even fitted with massive metal teeth so that they may rip their opponents' throats apart. All the Skitarii wear armour to protect their bodies, and in the event of sustaining injury, the adrenal high their augmented physiology casts them into and the pain suppresants they use prevent them from percieving any considerable feedback from even fatal injuries. High ranking Skitarii are also equipped with personal Void Shield generators. The Tech-Guard's appearance varies greatly, and depends on their origins and their masters -- some are uniformed forces, resembling in ways the Imperial Guardsmen, while others are great, hulking mounds of muscle, belligerent in conduct, their body armour not following a uniform template and designed, along with their physionomy, to induce primal fear in all who oppose them. A notable example of the latter are the Skitarii of the Legio Invicta, who, in addition to such feral appearance, are also richly dressed, clad feathered cloaks and furs of great beasts, wearing votive talismans and ivory ornaments and wearing helmets with feathered plumes. Regardless of these traits, however, the Skitarii will bear marks of allegiance -- symbols of their Mechanicus masters or the Titan Legion they serve.

Vehicles
The Skitarii are the armed forces of the Adeptus Mechanicus, the faction that produces and maintains virtually all vehicles and engines of war in the Imperium. As such, in addition to peculiar Mechanicus vehicles such as giant land crawlers, the Tech-Guard has access to every type of vehicle used in the Imperial Guard, Imperial Navy aircraft such as the Valkyrie, the Marauder, the Thunderbolt or the Vulture, and are known to have utilised the Rhino Armoured Personnel Carrier. It is unknown if the Skitarii make use of other vehicles employed by the Chapters of the Adeptus Astartes, though one can presume that it is possible, if their Forge World is industrious enough to outfit its forces with them and fulfil its production quota. The Tech-Guard, however, has no access to the Land Raider, as by the Emperor's decree issued in the Battle of Terra during the Horus Heresy, all these vehicles were transferred to be used solely by the Space Marines. Even though these times have passed, this ancient edict still remains in power. The Skitarii also do not utilise the Dreadnoughts, for obvious reasons.

Variants
Skitarii were generally divided into different types depending upon the role they were expected to play on the battlefield. The Executors Fetial, the Titan Legions' diplomats and ambassadors, are noted to possess many measures of combat conditioning that the Skitarii undergo, save for the rampant muscle mass increase and inducement of an adrenal battle trance, though it is unknown if they are considered to be Tech-Guard themselves.
 * Balisteria - The Balisteria were the artillery units of the Skitarii. The artillery used by the Skitarii ranged from Thudd Guns to massive Ordinatus pieces. The term Balisteria included both the vehicle or artillery piece, as well as the Skitarii crews manning them.
 * Cataphractii - The Cataphractii were the Skitarii's armour units. The Skitarii made use of everything from small armoured personnel carriers like the Chimera and Rhino to heavy combat walkers and super heavy tanks such as a Baneblade.
 * Classiarii - The Skitarii forces of the Adeptus Mechanicus take a variety of forms. On warships and Explorator vessels operating within the Koronus Expanse and the Calixis Sector, specially-programmed Skitarii are a necessity, for they serve as the members of boarding parties, security personnel and bodyguards where other forms of Skitarii would be impractical. Within the Mechanicus territories of the Calixis Sector, these warriors are known as Classiarii, a term of obscure meaning within the ancient traditions of the Calixian Mechanicus, believed to mean "mariners." Nigh-impervious to vacuum, fitted with thick, implanted armour, and equipped with an array of implanted weaponry designed for void combat and combat in the cramped enclosures of a starship, a Classiarius trooper is literally built for ship-to-ship combat.
 * Herakli - The Herakli were Skitarii heavy fire support specialists. These massive, vat-grown cybernetic soldiers were as large as Space Marines and were capable of carrying heavy laser weapons and multi-barrelled Autocannons with ease. The Herakli wore heavy red robes and cowls that were covered in Mechanicus sigils and were protected by thick ceramite amour plating that covered their chests and shoulders.
 * Huscarls - The Huscarls were the personal bodyguards of Skitarii officers and commanders, handpicked by these individuals and by them trained to perfection. The duty of the Huscarls was to protect the commander in the heat of battle and make sure that no debilitating harm is done to him.
 * Hypaspists - Hypaspist Skitarii were the most basic augmented infantrymen of the Tech-Guard and were armed with cybernetically hard-linked Lasguns similar to those used by the soldiers of the Imperial Guard. Hypaspists were generally more powerful and skilled soldiers than standard Guardsmen as a result of the cybernetic enhancements that made them stronger and more accurate than normal humans and the psychosurgery they had undergone to suppress their emotional reactions and make them immune to panic or fear. However, this enhancement also made Hypaspists less independent and able to think for themselves in combat.
 * Praetorians - The Praetorians represented the most elite troops to be found amongst the Skitarii. They were super-enhanced humans augmented by a wide array of cybernetics and integrated heavy weapons. However, many old Imperial sources also suggest that Praetorians are instead an elite Skitarii type similar to Imperial Guard Storm Trooper units, but possessed of advanced bionic augmentations, putting them somewhere in combat effectiveness and elite status between Storm Troopers and Space Marines. Some Praetorians are in fact a form of Combat Servitors, rather than living, cybernetic humans. They move on tank treads and are armed with powerful heavy weaponry, such as Plasma Cannons. All of these different variations of the Praetorian Skitarii are completely plausible, and based on the preferences of the Mechanicus Magi who build them.
 * Sagitarii - The Sagitarii were the Skitarii's heavy weapon specialists. These only include dedicated heavy weapons squads, as heavy weapons specialists attached to Hypaspist squads are still called Hypaspists.
 * Tribunes - The Tribunes are the officers of a Skitarii unit. Though all Skitarii ultimately bow to the authority of the Adeptus Mechanicus' Magi and Archmagi, these are all command personne found at the grand strategic level. The Tribunes handle the day-to-day tactical and strategic command roles for the Skitarii.
 * Venatorii - The Venatorii were created in the wake of the War of Brass that devastated the Skitarii Legions of the Lathe Worlds, leaving entire Forge Worlds of the Calixis Sector with virtually no troops left. The reigning High Fabricator started a discreet rearmament drive throughout the Calixian Forge Worlds. The more military minded Tech-priests were moved into position to help replenish the fighting ranks of the Mechanicus within the sector. It took many years to bring this grand plan together, but once everything was in place, the High Fabricator of the Lathes found himself with a new force consisting of some of the best-trained and best-equipped troops in the Calixis Sector. Dubbed the Venatorii, the new hunters were a force that was to remain separate from the recovering Calixian Skitarii forces and act as the true elite troops of the Lathes. With their unique organisation and frightening red armour, the few outside of the Mechanicus who were aware of their existence soon began to call them the Crimson Guard.

Protectors
The Protectors are a type of Skitarii comprised of genetically-enhanced humans drawn from the Adeptus Mechanicus' Menial underclass who serve as the personal bodyguards, law enforcement officers and fighting force for the high-ranking Adepts of the Mechanicus. They are often tied to the service of a specific Forge City on Mars or one of the other Forge Worlds. They differed from the standard Skitarii in several small ways, most notably because their faces were covered by a bronze skull mask with glowing green eyes and they were dressed in red robes the colour of old rust. They were noted to smell of spoiled meat and machine oils.

Notable Protectors

 * Rho-Mu 31 - Rho-Mu 31 was a Protector of the Forge of Magma City on Mars who served Mechanicus Adept Koriel Zeth, the Mistress of Magma City.

Dark Mechanicus Skitarii
Ever since the first betrayal on Mars during the Horus Heresy, the Dark Mechanicus and their Traitor Titan Legions have utilised the Skitarii under their commands to battle the forces of the False Emperor. They perform essentially the same function as their loyalist counterparts, protecting the domains of their masters and going to war at their bidding, with additional duties such as overseeing the slave workforce labouring on the Dark Forge Worlds. The Dark Mechanicus Skitarii themselves have become changed and mutated by the power of the Warp as much as their dark masters' twisted modifications.