Enginseer
Enginseers (Not to be confused with the Eldar Farseer or Spiritseer) are members of the Mechanicus. They differ from Tech Priests in that Enginseers are more combat orientated and are the only few members from the Machine Cult that hire themselves to other organizations. More predominantly they hire themselves to the Imperial Guard due to the amount of tanks and vehicles the Guard field out in combat.
Overview
Enginseers first and foremost are highly trained members of the Cult Mechanicus and are dedicated to the maintenance of Imperial technology. While Tech Priests may venture out and explore undiscovered locations for more goodies to hoard, Enginseers stay back to help other Imperial Organizations in order to maintain a stable relationship with the wider Imperium. They are a common sight on battlefields with large numbers of armoured vehicles, and are often accompanied by a retinue of servitors for assistance or protection. Although most Guardsmen revere their vehicles enough not to risk annoying an Enginseer by 'tinkering,' the modification of vehicles to fulfill a certain need is inevitable, much to the chagrin of any Enginseers present. Enginseer contingents are also included in the mighty Titan Legions and the crews of the massive warships of the Imperial Navy, allowing them to perform emergency repairs in the heat of battle.
Humorously 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 Quest for Knowledge. As a result of their overwhelmingly practical knowledge, they are often viewed as lowly but necessary cogs in the workings of the Cult.
Enginseers make use of robotic arm augmentations known as Mechadendrites that are connected to their central nervous system via the spine. They are used to help the enginseer in repair operations, heavy lifting and for self defense.