In the game Warhammer 40,000, the Daemonhunters consist of the Ordo Malleus and their militant Chapter, the Grey Knights. The Ordo Malleus is a division of the Inquisition which for thousands of years have waged a covert war for Humanity's survival. Every Inquisitor has sworn with his life to defend the Imperium from its worst enemy and to destroy the physical manifestation of Chaos itself: the Daemon. A Inquisitor of the Ordo Malleus has at his disposal all the Imperium may offer. He will not hesitate to recruit local troops at a moments notice. He is even able to call upon the might of the Space Marines.

When the level of Daemonic infestation is so much that an Inquisitor can not handle it alone, the Ordo Malleus calls upon the Grey Knights. Surpassing even their fellow Space Marines in power, the Grey Knights can purge Daemonic filth that outnumbers them many times over. They use psychically-enhanced weapons and total fearlessness in the face of Chaos. Without the Ordo Malleus and the Grey Knights the Imperium would not survive.