Ordo Malleus is a division of the Inquisition filled with the most exceptional and fearless warriors dedicated to slaying Daemons and heretics, warriors of the chaos. The "hammer" of this section are the ferocious warriors known as the Grey Knights. It is a tale that during the Second Founding the Emperor himself ordered the creation of a new Space Marine chapter, number six-hundred and sixty-six in secrecy in order to create incorruptible warriors to protect mankind from the creatures of Chaos. These Space Marines, known as the Grey Knights, set up their fortress on Saturn's moon known as Titan and drew their gene-seed directly from the Emperor's flesh and blood.

Grey Knights are plucked up from the most feral of worlds and are only even considered if they control exceptional psychic potential. Upon reaching Titan, these warriors undergo the beginnings of becoming a Space Marine and begin their training. Becoming immune to the fear and horror that would affect even a 'normal' Space Marine, the Grey Knights finish their training and would gladly give their life in defiance of the daemonic. Donning the Nemesis Force Weapon and Storm Bolter, these warriors lunge themselves into battle, in Power Armor or the Tactical Dreadnought Armor known as Terminator Armor.

The Daemonhunters also reach out for allies out of other pockets of the Inquisition. Using Space Marines and Inducted Imperial Guard, and even the Sisters of Battle, the Daemonhunters can rally quite the diverse force. However, the heart of the Ordo Malleus lies within the Grey Knights and their duty to protect.

A Daemonhunter can consist of many different forces, though I will merely focus on one that is centralized upon the Grey Knights. First and foremost, there are many special rules that effect a Grey Knight.

• As Grey Knights are forged to be immune to fear, they are all Fearless.

• Grey Knights may also teleport if in Terminator Armor or in a Teleport Squad.

• Grey Knights have the True Grit special rule if and only if they are in power armor and wield a storm bolter. True Grit means that Grey Knights count as having a pistol in close combat, meaning they get an extra attack if they have another close combat weapon (they almost always will with Nemesis Force Weapons and Storm Bolters). However, Grey Knights do not receive an attack bonus for charging if they use the Storm Bolter like this. In essence, Grey Knights in Power Armor add +1 to their attacks with their default equipment but do not gain a charge bonus attack.
• The Aegis means that any psychic power that targets a Grey Knight squad may be resisted as if that squad had a psychic hood (ie Leadership + D6. If the Grey Knights are higher, the roll is canceled). Use the highest leadership value in the squad.
• The Shrouding gives Grey Knights a weak Night Fighting rule. Any enemy unit firing at a Grey Knight squad must roll a 3D6 and multiply by 3. If the Grey Knight squad is within this range, they can be spotted and things continue. If they fail to see, the unit firing loses its chance to fire this round. Barrage and ordnance weapons fire as normal if not spotted but double their scatter. A unit with a psyker may re-roll this spotting check and accept the second value.
• The special rule called Rites of Exorcism says that all daemons attempting to charge a Grey Knight squad counts as if they were charging through difficult terrain.