- "A heretic may see the truth and seek redemption. He may be forgiven his past and be absolved in death. A Traitor can never be forgiven. A Traitor can never find peace in this world or the next. There is nothing as wretched or as hated in all the world as a Traitor."
- — Anonymous
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 combatting 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". Mutants, rebels and Heretics are also targeted by the Ordo Hereticus. The Ordo has no qualms at all about acting against threats in the other Adepta and many a Renegade Adeptus Ministorum Cardinal or corrupt Tech-priest has met his end at the hands of a Witch Hunter. 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. The members of the Ordo Hereticus can also call upon the military forces of the Ecclesiarchy, the Frateris Militia.