"Sin, crime, and heresy are malfunctions within the mechanism of civilisation, the evidence of some faulty cog within the grand machine of society. A repair necessitates the removal of these errant components, either to forge them anew in some useful form, or so that they may be eliminated as imperfections."
- — Excerpt from Chapter XIII of "Observations upon the Ordered Function of Empire"
The Magos Juris are those rare Tech-priests who 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. Amongst their colleagues on the Calixis Sector's Forge Worlds, these individuals are sometimes known as Magos Juris. They relentlessly pursue those who would commit tech-heresy or steal the secrets of the Adeptus Mechanicus.
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. Worse still are those who smuggle technology, attempting to keep it from its rightful guardians.
The fate of such men, when they are caught, is a grim one, for they are condemned to spend a far-expanded lifetime toiling without mind or will as a Servitor aboard the starship of the Magos that judged them, their minds obliterated and their bodies repurposed to serve the Machine God that they blasphemed against. There are many Explorator Tech-priests who speculate that the Magos Juris are, in fact, the agents of a secret order within the Adeptus Mechanicus known as the Lords Dragon.
This ancient and powerful cabal is composed of specially-altered Archmagos said to exist deep within the secret inner circles of Mechanicus politics on the Calixian Forge Worlds known as the Lathes. Their task: to police the Mechanicus from within. However, little evidence can be found that proves the Lords Dragon exist at all, and that these Magos Juris do not simply operate on their own.
- 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 battle in the cramped enclosures of a starship, a Classiarius trooper is literally built for ship-to-ship combat.
- Lathe Pattern Murder Servitor - Commonly used aboard starships to supplement boarding parties and raiding forces, Lathe Pattern Murder Servitors are ghoulish, skull-masked killing machines. The Lathe Pattern, developed on and favoured by the augment-artisans of the Forge Worlds of the Calixis Sector known as The Lathes, is a hunched, predatory monster, driven by sadistic and aggressive Machine Spirits. Mono-talons and viscerator-limbs allow them to tear apart most living foes, while their Melta-cutters burn through bulkheads and destroy equipment. Designed to intimidate as much as to kill, Lathe Pattern Murder Servitors are consummate hunters, stalking their prey and moving with inhuman speed. If not ordered otherwise, they spend hours hunting any living creature not programmed into their spoor-targeters, undeterred by any obstruction and unhindered by fear or humanity. Their nature is intended to inspire dread, from their chrome skull-masks, long, razor-sharp talons and steel weapon-limbs, to the electronic howls and moans of their Vox-boosted throats.
- Ryza Pattern Plasma Pistol
- Sollex Pattern Omnissian Axe
Notable Magos Juris
"It is rare indeed to find a kindred spirit, a man whose devotion to all that is right and proper knows no limit nor restraint. Too many of those who maintain the purity of the Imperium quail at the prospect of the necessary acts involved. It is gladdening to see that some still remain who will not hesitate to spill the blood of the innocent so that the guilty may be justly punished."
- — Witch Hunter Calan Rykehuss, Ordo Hereticus
- Magos Juris Konstantyn Ambolic - Konstantyn Ambolic long ago suffered near-fatal injuries after a confrontation with a cell from the Heretek organisation known as the Logicians. Scarcely little more than scraps of flesh sustained by arcane machinery, Konstantyn was rebuilt thanks to the skill of his colleagues, though his resurrection resulted in his being shorn of all remaining human emotion save for a fierce loathing for Hereteks. Soon after, he took up the mantle of a Magos Juris, and began to methodically hunt every Heretek known to the Adeptus Mechanicus leadership within the Calixis Sector. In the four centuries since the beginning of his crusade, Ambolic has been responsible for capturing hundreds of Hereteks, leaving a trail of destruction in his wake. Ambolic has little consideration for the lives of either his servants or the teeming masses of humanity, and will do whatever he deems necessary to accomplish his goals, an attitude that has won him allies amongst the most hard-line of Magi and several extremely ruthless Inquisitors. Ambolic is almost entirely without emotion, his scorn for criminals aside, and fears nothing. His cybernetic body is extremely resilient and fitted with additional armour plating to further reinforce it, allowing him to shrug off all but the most potent of attacks without difficulty. His appearance is carefully engineered to intimidate, and the sight of bullets and lasbolts pattering ineffectually from his metal skin only adds to the dread he inspires amongst those he chooses to confront personally. His sophisticated vessel, the Omnissiah's Vigil, which utilises ancient technologies that include advanced targeting systems and plasma reactors, is well-suited for pursuing Heretek starships across the sector, and crushing them when the pursuit is over.
- Rogue Trader: Hostile Acquisitions (RPG), pp. 85-88