The forges of Mars were highly prized during the Horus Heresy – a weapons factory on the doorstep of Terra was both a tempting target for Traitors and a point of concern for those defending the seat of the Emperor’s power. Many Tech Priests broke the strictures of the Cult Mechanicum and engaged in profane tech-heresy, but the zealous worshipers of the Machine God are not without their ranks of judges and accusers, such as the Arcuitor Magisterium.
Magi and high nobles of the Cult Mechanicum who demonstrate a particularly inflexible approach to the dogma of the Omnissiah are most likely to be elevated to the status of Arcuitor. These individuals tend to be ancient beyond belief, augmented to the point of inhumanity as part of their never-ending quest to become as close to the perfect Machine God they worship.
Though they are not deployed by the Prefecture Magisterium in an official capacity, their cachet and notoriety allow them to call on great resources when pursuing their zealous agenda, enough even to mount their own personal crusades against those they believe to have transgressed into tech-heresy.
Hunting down Dark Mechanicum operatives and renegade Tech-Priests is busy work even for someone with a technologically enhanced brain and a surfeit of mechanical limbs, and so it is not uncommon for an Arcuitor to be attended by a scribe to aid them in their duty.*
The Arcuitor Magisterium is made from Forge World resin and has rules in the Liber Mechanicum – Forces of the Omnissiah Army Book, where she can make use of her influence to bring along a Maniple of Arlatax Battle-automata or Vorax Battle-automata without taking up a Force Organisation slot.
* Honestly looking at this little guy is like looking in a mirror.
