Officio Assassinorum
"Ask not for whom they seek, lest it be thyself." - Tactica Imperium on The Officio Assassinorum
When the shit hits the fan, these are the guys that get their hands dirty. It's all about the wetwork. This branch of the Imperium recruits, trains and commands Assassins, for more information on the individual Assassin types, please visit this page.
You can tell you don't mess with the Officio Assassinorium when their official description is, "Ask not for whom they seek, lest it be thyself;" this basically means ANYONE, from the lowliest of workers to the High Lords of Terra, at ANY moment, is open to either having their brains spilled on pavement by a sniper round, their spleen torn out by screaming Wry-man, or shanked by dear old mum for no apparent reason.
History
The Officio Assassinorum was founded at the beginning of the Great Crusade as a department for holding any up-and-coming warlords or heretical leaders accountable for their actions. And by "accountable" we mean "disposed of." And by "disposed of" we mean "killed stone dead." Formed by Malcador the Sigillite and the six masters of the Clades (the future temples), it was founded in extreme secrecy in an attempt to keep it out of the Emperor's knowledge and maintain his purity (a concept the Big E always found funny). Technically, a terminatus order can only be issued by the Senatorum Imperialus (AKA the High Lords of Terra), and the members of the Officio Assassinorum are kept on a very short leash. Unlike the Inquisition, they have no discretionary powers of their own.
The head of the Officio is known as the Grand Master of the Officio Assassinorum, or The Master of Assassins, who sits alongside the Fabricator-General of Mars and the Ecclesiarch of the Adeptus Ministorum as one of the High Lords of Terra.
Which, if you think about it, must be somewhat distracting during their meetings. The Lords are sitting around and discussing the fates of trillions of men, and as the debate goes back and forth, one of them says nothing, ever. He just sits there, smoking a lho-stick with his trench coat wrapped around him, almost completely overlooked. And then they remember that a bad decision could get them killed, and this is the guy who does that. And only that. His only job is to dispatch death on swift wings to any high official. It'd be like having a guillotine built into your throne. the Sword of Damocles hanging over your head everywhere you went.
Members are recruited at a very young age; most of them are children from Feral Worlds or are taken from the schola progenium. Recruits are biologically augmented and trained at the School of Assassins on Holy Terra for ten years before being assigned to one of the Assassin Temples to continue their training and eventually serve the Imperium.
The Assassin specialists approach Chuck Norris levels of awesome, as the Temples have permission make use of "any means or tools to get the job done," even if it means banned tech from the Dark Age of Technology(like 'synskin') or xeno artifacts (like the C'tan phase blade). These Assassins are also given crushingly restrictive psych treatments to ensure they never use these tools except when ordered, which can make them seem kinda spastic during downtimes when said tools are augmentations to their own body.
There are only 2 recorded examples of anyone in the Officio turning against the Imperium. Unfortunately, both times it was the Grand Master, Drakan Vangorich (goes to show, never trust a Russian). The Imperium learned of the first one's butthole treachery when he had the High Lords of Terra wiped out to the last man. Very grimdark, though the uncaring dicks had it coming to them.
After that betrayal, an Astartes retribution force was dispatched to "resolve" the situation. It is not known how many marines were sent; since the force was made up of elements of three chapters (Halo Brethren, Sable Swords and Imperial Fists), it was probably at least 1000 marines. As soon as they landed on Terra, the commander of the force was assassinated. The remaining marines broke into the grand chamber of the Assassinorum Temple and found 100 (!) Eversor Assassins between them and their target. A single marine survived to plug the Grand Master in the brain with a boltgun. This super-hardcore-awesome-ass-kicking marine was definitely Darnath Lysander.
The other one was Vindicare Assassin LIIVI.
Ha, just kidding. The second time was during the Age of Apostasy in M36, when the Grand Master was himself assassinated by a Callidus Assassin under the orders of Goge Vandire, the insane ruler of the Imperium. Of course, you don't become Grand Master without being an Assassin yourself, and it turned out that he had switched places with a body double. What followed was a civil war within the Assasinorum to mirror the one wracking the Imperium, and ended up filling the Imperial Palace with nerve gas and destroying entire wings of Mankind's greatest fortress with ancient Dark Age and xenos weaponry. Eventually, the Grand Master triumphed, but went into self-imposed exile at the end of it, and might still be alive today. After the war, the Inquisition set up the Ordo Sicarius to monitor the Assassins and make sure they stay in line.
Alas, they will always be second best, for they can never become Ultramarines. They only exist in fluff for the purposes of showing just how bad-ass a specific enemy is. For example, during the Horus Heresy, eight Assassins, at least one from each temple, was sent to form an Assassin's Justice League of Doom and kill that asshole who started it. For SOME REASON, like everyone else in the Imperium who tried to stop it, they failed. Also, the same thing was tried during the Medusa V campaign, to assassinate the leader of the Chaos faction, and seven of them failed. This is known as the "Worf Effect."
Divisions
The Officio Assassinorum has six "temples," or specialist branches, each focused on one particular method of assassination:
- Callidus - shapeshifters, masters of infiltration. All women.
- Culexus - soulless gothtards that are invisible & immune to psykers, daemons & the Warp.
- Eversor - cyborg, drugged-up killing machines that have two settings: coma and RIP'N'TEAR!!1!!1!one!
- Vanus - leet hacker NERD CHESS PLAYERS. All are geniuses in the fields of intelligence gathering, strategy and JUST AS PLANNED. "The cleanest kill is one that another performs in your stead with no knowledge of your incitement." They are what every neckbeard wants to be.
- Venenum - master poisoners who can take the things found in a kitchen and kill a Space Marine with the resulting mixture.
- Vindicare - snipers that can "BOOM! HEADSHOT!" from the horizon.
- Maerorus - a failed attempt at creating a living weapon able to operate without support or equipment for a prolonged period of time; the only one known to exist proved to be impossible to control and went rogue. Think Alex Mercer from Prototype, only even more sociopathic.
Death Cult Assassins aren't part of this framework; there are thousands of death cults throughout the Imperium and they each train in their own way to kill enemies of the Emperor, but are not officially-sanctioned and are more autonomous than the Assassins.
