Engineseer Auxillia were those acolytes and adepts of the Mechanicum that operated in a technical support role for the Imperium of Man's armed forces at the time of the Great Crusade and the Horus Heresy, often accompanying their masters and the mighty war machines they administered onto the battlefield, albeit at a safe distance if possible. In doing so, they were on hand to make field repairs, assuage fevered Machine Spirits and perform the required micro-calibrations to arms and systems needed to ensure the holy engines of battle performed to their optimal efficiency. Although the safety of the Auxillia was considered secondary to their sacred charge, they were armed to defend themselves as needed and often carried fearsome firepower of their own drawn from the armouries of the Mechanicum.
- The Horus Heresy - Book Two: Massacre (Imperial Armour) by Alan Bligh, pg. 271