The Ephesian Schism
The Ordo Hereticus is one of the three major orders of the secretive organisation known as the Imperial Inquisition. They are tasked with protecting Mankind from itself, by combating such internal threats to the Imperium as treason, mutation, heresy, apostate members of the Ecclesiarchy and unsanctioned psykers, better known as “witches”.
It is this latter function that has earned the Inquisitors of the Ordo Hereticus the name “Witch Hunters.” These Inquisitors are some of the most feared individuals in the entire Imperium, and like all Inquisitors they have ultimate authority over any other Imperial organisation in the Adeptus Terra and can demand assistance from any other source of authority in the Imperium. The Inquisitors of the Ordo Hereticus are generally considered darker and more sinister than their Ordo Xenos and Ordo Malleus brethren because of their focus on eliminating the human enemies of the Imperium, which have transformed them into a grim, paranoid and unforgiving lot.
The Ordo Hereticus’ Chamber Militant are the Sisters of Battle, the Orders Militant of the Adepta Sororitas, and they also make use of the Inquisitorial Black Ships to round up unsanctioned psyker mutants from across the galaxy and can call upon the military forces of the Ecclesiarchy, the Frateris Militia.