A Discipline Master was a specialist often utilised by some Imperial Army regiments during the Great Crusade and Horus Heresy eras of the 30th and early 31st Millennia. These stern task masters were responsible for maintaining discipline within the regiment to which they were assigned. They were also responsible for tracking down Imperial Army deserters that repudiated their oaths to the Emperor of Mankind and shirked their soldierly responsibilities.
Discipline Masters were known to use hunting eagles to help them track their prey. Their fanatical dedication to the service of the Emperor overrode any feelings of compassion, mercy or humanity when carrying out the summary executions of those found wanting, for which they employed a ceremonial Electro-scythe.
The Discipline Master proved to be the precursor to the Commissars of the Officio Prefectus who now serve with every regiment of the Astra Militarum, the descendant of the Imperial Army following the Reformation of the Imperium after the Horus Heresy.