Officio Assassinorum

In the fictional Warhammer 40,000 universe, the Officio Assassinorum is an Imperial agency that trains and employs different assassin temples to further the goals of the Imperium of Man. Although the Inquisition strikes fear in the hearts of all Imperial citizens, loyal and corrupt alike, the deadly disciples of the Officio Assassinorum strike fear in the hearts of even the most savvy, battle-hardened of warriors.

Assassins are typically deployed alone wherever feasible, having been trained to operate extensively behind enemy lines with no support. Given the sheer political power of the organization and the fact that its operatives are known to have been used against rival High Lords, the authorization to assassinate a target must come from the highest echelons of Imperial command. For this reason, Assassins are wached very closly to make sure that they are under the control of the imperium.

Temples
There are six major Assassinorum 'temples', each specialising in a different form or method of assassination;

Callidus Temple
Assassins of the Callidus Temple use deceit and trickery to accomplish their objectives, usually assisted by the shape-changing Polymorphine drug.

The vast majority of missions undertaken by Callidus Assassins involve infiltrating a Chaos cult or other heretical organisation, in order to kill the leader along with other key members of the cult. Once the leadership of such a group has been removed, it is easier for armed forces to eliminate the cultists, without having to resort to extreme measures such as Exterminatus.

However, less frequently, Callidus Assassins are also called upon to undertake more exotic assassinations, requiring the use of both polymorphine and surgical implants to allow them to assume the form of a wider range of humanoids.

Although they are not typically fielded with a larger army on the field of battle, Callidus Assassins can be deployed behind enemy lines in order to infiltrate facilities such as bases or encampments and take out enemy leaders or key personnel. This is usually achieved by the assassin killing an isolated patrol or enemy unit and then assuming the form of one of those slain through the use of polymorphine (also acquiring the armour and wargear of the deceased to complete the disguise).

Callidus Assassins are the most secretive and least well-known of the Assassins, as their usefulness would greatly diminish if their capabilities were more widely known. They are usually tasked with their missions by the Inquisition, especially the Ordo Hereticus, although as stated above, less frequent missions from the other Orders are also undertaken.

The most important feature of the Callidus Assassin is the use of polymorphine to enable them to assume the features of any human (of whatever gender). This then enables the Assassin to infiltrate organisations or bases and eliminate their assigned target. The Callidus Temple is highly skilled in this area, and often their work is not detected until the Assassin has already made a clean getaway. Accordingly, their weapons are predominantly close combat weapons, as their infiltration skills enable them to get very close to the target before they need to act. This is assisted by their signature weapon, the C'Tan Phase sword, a "living metal" weapon which can be concealed easily, and is capable of bypassing any protection, even energy shielding. Callidus also carry a large number of small poisoned blades and an exotic Neural shredder, a short ranged weapon which savages the nervous system of its targets.

The Callidus Assassins usually impersonate someone in a close position to, or holding influence with, the target (for example, a trusted advisor to a Chaos Lieutenant, or the nursemaid to a child prophecised to cause much pain to the Imperium). With the addition of implants and surgical alterations, Callidus Assassins can impersonate members of alien species, including, Kroot, Ork, and in at least one case, Genestealer. The implants are often permanent, and restrict the Assassin solely to impersonations of that species. It should be noted that Eldar, Dark Eldar, and by inference most likely Tau can be mimicked without implants.

Culexus Temple
The Culexus Temple are one of the most sinister and feared orders of the Officio Assassinorum and have been described by Eldar warlocks as nothing short of pure evil.

Those chosen to be Culexus assassins are born with the rare Pariah gene, which means they do not have souls or presences within the Warp. Even normal humans (friend or foe) find the presence of a Pariah extremely disturbing, but the effect is most pronounced on Psykers, who find them genuinely terrifying, as though staring into a hole in the universe. They can nullify psychic powers, and if in close quarters their very existence drains the souls from psykers. Culexus assassins therefore specialise in psyker hunting, most notably of Eldar warlocks and rogue psykers. Culexus assassins have also been shown to be useful at combating daemons, as Daemons are entirely made of psychic power.

Their most notable piece of equipment is the Animus Speculum, a stylized helm which conceals much of their soulless nature, but during battle the arcane 'eye' of the helm opens, bringing their full terrifying abilities to the fore. The Animus fires bolts of negative psychic energy, and can drain nearby psykers to increase its power. They also use the exotic psyk-out grenades which induce psychic feedback in their targets. Finally, the Culexus carry an Etherium, which induces confusion and disorientation, making it near impossible to target the assassin with weapons. Due to the fact that any nearby enemy is already disconcerted by the soulless Culexus, this makes him extremely difficult to target.

Not much is really known about the internal goings on in the Culexus Temple. There is a belief that the Pariah gene was implanted in the human race by the Necrons eons ago for use as weapons against psykers, in response to the creation of psychically-charged races bred by the Old Ones to fight the Necrons.

Vindicare Temple
The most prominent feature of the Vindicare Temple is that it trains its subjects to near-perfection in the art of marksmanship; they aim to take out the Emperor's worst enemies with a single bullet. Vindicare Assassins are also trained in stealth and evasion techniques as well as marksmanship in order that they may get into the most advantageous position from which to make their shot. The idea behind this is that a kill can only be made from the best position. Indeed, Vindicare Assassins have been known to occupy a position for days, or even weeks, before taking their shot.

The Vindicare are often employed in eliminating individuals who are suspected of harbouring daemonic entities. The hopes are that they can eliminate the host before the daemon is able to manifest itself on the material plane. Characters of great charisma, false prophets and false messiahs among them, have fallen to the Vindicare's bullet, most commonly whilst they are preaching their false beliefs to their followers. Upon this swift, brutal, and yet simple death, the erstwhile followers soon become disheartened and afraid. Countless heresies have been prevented with a single, well-aimed shot where legions of men would have failed.

Vindicare are armed with their trademark Exitus rifles, loaded with standard high power ammunition as well as several more exotic shells. These include shield-breaker rounds which can bypass shielding, Turbo-penetrators that can pierce a heavily armoured tank, and Hellfires which carry a potent mutagenic acid into the target. They wear Stealth suits that mask their visibility in every spectra, and sophisticated Spy masks that allow them to pick out their target no matter the light level or cover. They also carry high powered Exitus pistols for close quarter work.

Occationaly Vindicare are also employed to take on demolition work, such as destroying an artillary battery or taking out a siege factory. In these cases the assassin utilizes the same stealth and remoteness that he does in sniping his target, usually using remote charges and incendiary shells.

In Relic's hit real-time strategy game Dawn of War: Winter Assault the Vindicare Assassin (called the Assassin in the game) is the Imperial Guard's only infiltrator unit, armed with a high-powered sniper rifle as in the tabletop game. Imperial Guard Commanders can temporarily double the range and damage of the Vindicare's sniper rifle by ordering the unit to activate the rifle's Assassination Scope for a limited time (as prolonged use of the scope causes the rifle to overheat). It can take out most infantry with a single headshot, and can in certain cases snipe the drivers of a light vehicle.

Eversor Temple
The Eversor is possibly the most gruesome of the many temples of the Officio Assassinorum. The Eversor specialise in shock and terror tactics, instilling fear of Imperial retribution into the hearts and minds of all who hold positions of power. In the employ of the Ordo Malleus, Eversor Assassins are used when the indelible taint of Chaos is believed to have spread throughout the ruling elite of an entire organization.

Whilst the more overt forces of the Ordo Malleus face the daemonic minions of a Chaos cult on the battlefield, the Eversor will operate behind enemy lines and eradicate the infection at its source. An Eversor rarely has just a single target. His mission will be to rip the heart out of the Chaos insurgency, wreaking havoc and destruciton. Such brutality ensures that the renegades are totally cleansed and that no would-be successors may take over. The sheer terror left behind in the wake of the Eversor's onslaught ensures that none will dare to oppose the Imperium again.

In many ways an Evesor assassin has more in common with a bomb than with an assassin. Rather than taking out a single target, the Eversor is usually employed to clear a large number of targets in a short amount of time. In fact; because of the masses of drugs running through their bodies, when an Eversor is brought down in combat, the drugs will react violently and cause the Eversor's corpse to explode. In order to act so efficiently, the Eversor is fielded with a wide variety of weapons and tools including a pistol that can fire neuro-toxin coated needles, powerful melta bombs for destroying tanks and heavy doors, and a potent chemical cocktail that gives the assassin incredible reflexes and a single minded rage.

Others
There are two more major temples that do not have miniatures in the game, and thus not much information about them has been compiled into official sources. One of them, Venenum, deals in assassination through poisoning. Of the other, Vanus, nothing is known (the Latin word "Vanus" means "Empty"). Though this is most likely to allow players to create their own temple in an attempt to "fill in the gaps" and give the game a more custom feel.

The Officio Assassinorum also maintains patronage over numerous minor assassin temples and death cults.