In its earliest days, the XIXth Legion was used for infiltration, reconnaissance, and target identification operations. The Legion was covertly used to quickly annihilate any faction which refused to submit to the new [[Imperium]], striking from the shadows without warning. The XIXth used terror tactics similar to the [[Night Lord]]s.{{Fn|13}} One of the earliest known campaigns by the Legion was the conquest of the central Asiatic region, which was ruled by a tyrant known as [[Kalagann of Ursh]]. They won many battle honours on Terra, and later took part in the expansion of the Imperium into the rest of the [[Sol System]], liberating [[Jupiter]]'s moon of [[Lysithea]] from [[xenos]]. The battle on Lysithea proved costly for the Legion and veterans of the battle wore Jovian runes in its commemoration for many years after.{{Fn|30a}}

Before the discovery of [[Corax]], the Raven Guard utilized utilised terror tactics similar to the [[Night Lord]]s. However, when their Primarch was discovered, he was disgusted with these methods and introduced changes.{{Fn|13}} Following the discovery of [[Corax]] the Raven Guard, based upon his teachings, became masters of sabotage, assassination, and other covert operations. Planets that were thought impossible to take, fell quickly as the Raven Guard applied precise military pressure to its vulnerable sectors.{{Fn|2a}} Such was the Legion's reputation that [[Warmaster]] [[Horus]] frequently requested their assistance to assure victory, though there was little admiration between the two; unconfirmed reports include the two sides nearly coming to blows on one occasion.{{Fn|2a}} In addition, Corax displayed a consistent ill-favour and mistrust towards veteran warriors of his Legion born of [[Terra]], as opposed to those native to [[Deliverance]].{{Fn|31b}}

Tensions between the two boiled after over during the [[Battle of Gate Forty-Two]], where Horus had the Raven Guard launch a bloody frontal assault on enemy defenses that decimated the Legion's numbers despite Corax's warnings that the plan was reckless beforehand. After the battle, the Raven Guard was reduced to 80,000 Astartes. Corax removed his forces from Horus' command, bitterly swearing to never serve alongside the Warmaster again.{{Fn|30a}} He also began to send his Terran-born forces into forgotten [[Crusade]]s on the galactic fringes, ensuring in his eyes that the Raven Guard remain "pure".{{Fn|31b}}

The Raven Guard legion was one of the smallest legions during the [[Great Crusade]], numbering 80,000 Astartes as well as an [[Imperial Army]] [[Regiment]] known as the [[Therion Cohort]] attached to the legionLegion's expeditionary force.{{Fn|30a}} As a legion they were a fierce enemy for anyone who opposed the [[Imperium of Man]], using time honoured tactics of guerrilla warfare which Corax himself had learnt during the Revolution he himself had commanded to free his people from the merciless [[slavery]] forced upon them by the Tech Guilds of [[Kiavahr]].{{Fn|2}} Extremely efficient and well trained, the Raven Guard would engage in acts of mass sabotage along with infiltration, blink-of-an-eye Strikes, strikes and expert covert operations, all of which they had perfected into what would look like ease to any other warrior.{{Fn|2}}

The Raven Guard was one of seven legions to be sent to the Istvaan system (Others present were the [[Iron Hands]], [[Salamanders]], [[Alpha Legion]], [[Iron Warriors]], [[Night Lords]] and [[Word Bearers]]) to quell a rebellion lead led by the former [[Warmaster]], [[Horus]] — [[Primarch]] of the [[Sons of Horus]] Legion (Formerly the [[Luna Wolves]]). Horus and his other three traitor primarchs ([[Fulgrim]], [[Angron]] and [[Mortarion]]) had entrenched themselves on the planet of [[Istvaan V]], and lay in wait for the Loyalist forces to land and engage. The fighting once joined was fierce and hot-blooded, brother versus brother, and no quarter was given on either side. Mid way into the fighting, Horus and his allies retreated back into their fortifications for no reason that could be grasped by the loyalist factions. The Raven Guard were in the thick of the fighting from the start, though out of their element due to the lack of tactical planning and the close-up-and-personal combat spreading like wildfire across the plains of Istvaan V. They fought both with as much honour and as much skill as any other legion would in the circumstances. When the traitors made a surprise withdrawal back to their fortifications, the Raven Guard used this cease break in the fighting to regroup and re-arm.{{Fn|2}}{{Fn|12a}}

The Raven Guard homeworld is [[Deliverance]], a moon which their Fortress Monastery "[[Raven Spire]]" is built on. Deliverance was once known as Lycaeus, where 10,000 years previous to current events, Corvus Corax (soon to be [[Primarch]] of the Raven Guard Legion) lead led a revolution to free his fellow slaves and eventually the whole moon from the slavery forced on them by the tech guilds of the planet below, [[Kiavahr]].{{Fn|2}} Kiavahr was converted into a forge world by the [[Adeptus Mechanicus]] upon the [[Emperor]]'s arrival, due to [[Corax]]'s wish that the tech guilds no longer hold sway; this meant that the [[Space Marine Legion|legionLegion]] also received a vital supply line for materials.{{Fn|12d}}

Since the earliest days of the Raven Guard, some of their number have been prone to a battle madness known as the '''Sable Brand'''. This consists of cold-blooded determination to fight on with no regard for self-preservation coupled with an inability to separate the whispers of the dead from the words of the living. Thought to be an original flaw in Corax's gene-seed that he himself may have suffered, it is marked by one's eyes becoming completely black. Though its effects are not permanent, it is often ever-present amongst those who suffer from it. During the [[Great Crusade]], Corax organized organised those afflicted into units of Shadow Killers. However, after the Legion's near extinction on [[Isstvan V]], the Primarch could no longer waste troops like this.{{Fn|36g}}

After Isstvan V, Corax labored laboured with various methods to control the Sable Brand. He developed the [[Trifold Path of Shadow]] as a result in an attempt to control the outbreaks of madness. The doctrine has indeed led to fewer battle-brothers becoming afflicted with the Sable Brand. However, should the afflicted not be slain in battle, they are eventually incarcerated in the [[Ravenspire]] and used in experimentation by the Chapter's [[apothecaries]]. This attempt to cure their gene-seed is carried out in total secrecy.{{Fn|36g}}

Because of their hit and run tactics and sowing confusion in enemy ranks, the Raven Guard also make extensive use of [[Assault Squad]]s as well as any other formation that uses [[Jump Pack]]s.{{Fn|55}}. The [[Tactical Squad]]s of the Raven Guard are often deployed via [[Thunderhawk]]s or [[Drop Pod]]s. The favourite weapons of the Raven Guard [[Space Marine Commander|Commander]]s are the [[Lightning Claw]]s and it is a common sight that their command squads also come equipped with these weapons in addition to their [[Jump Pack]]s.{{Fn|2}}

Raven Guard Captains are fiercely independent, and it's incredibly rare for the chapter to fight as a whole. Individual companies are completely autonomous and are quick to lend their aid to Imperial commanders across the galaxyGalaxy, with or without the sanction of their Chapter Master.{{Fn|2}} Such behaviour has led to some to question the Raven Guard's soundness, but most recognise that such fluidity of command proves the presence of formidable discipline, not its absence.{{Fn|4a}}

[[fileFile:TauVsRavenGuards.jpg|thumb|right|350px|Raven Guard assaulting Tau T'au position]]Core to Corax’s teachings was the '''Trifold Path of Shadow''', often rendered in pictorial form as a short-bladed trident or triple-bladed lightning claw.{{Fn|36e}} The first path of shadow is Ambush,{{Fn|36e}}, the second Stealth,{{Fn|36f}}, and the third Vigilance.{{Fn|36g}} Mastering one Path, he taught, brought the possibility of victory; mastery of two rendered triumph likely, and accomplishment in all three made the foe’s defeat all but inevitable. From the beginning, the chapter’s Chapter’s battle companies were based on this Trifold Path. Companies 3 through 5 each specialised in one branch, and a battle-brother’s promotion to the 2nd came only when true mastery was attained. Such promotion is far from guaranteed. Even amongst Corax’s sons, there are few who can replicate his skill so completely, and many battle-brothers live out a life of war in the same Battle Company, peerless in their own path, but never truly able to grasp the fathomless depths of the others.{{Fn|36e}}

Due to their specialised combat style, the Raven Guard makes less use of heavier vehicles and tanks (such as the [[Land Raider]] and [[Predator]]) than most chapters.{{Fn|3}} However , they conversely make heavy use of [[Land Speeder]]s and gunships, and due to their extreme tactical autonomy and genetic instability nearly every deployment with see an [[Apothecary]] of some sort of included. As a result, the Raven Guard maintains more Apothecaries and [[Helix Adept]]s then than most chapters.{{Fn|43a}}

[[Image:RGvsTau.jpg|thumb|right|300px|Raven Guard battle the [[TauT'au]] ]]The Shadowmasters or [[Mor Deythan]] were a unit of Raven Guard during the [[Great Crusade]] and [[Horus Heresy]]. They were ordinary battle-brothers who had [[Corax|their primarch]]'s ability to '''Shadow-walk'''. It was a quirk of the gene-seed in a few [[Deliverance|Deliverancian]] born Raven Guard that had more than just the standard gene code. One unique trait about of the Shadowmasters is that they were completely unknown to their own legionLegion. The marines were selected for testing "Thermal Technology" which was considered "highly temperamental". Corax and select apothecaries were the only marines in the legion Legion that knew of the group at the time of the [[Horus Heresy]]. The Mor Deythan acted as an elite stealth team and saboteurs and communicated through [[Stalk-Argot]] while working in concert with the rest of the legionLegion. The Shadowmasters performed flanking manoeuvres and sabotaged columns of rogue [[Skitarii]] on [[Constanix II]].{{Fn|18}}

The '''[[Moritat]] Protocol''' dates back to the Horus Heresy, and sees individual Raven Guard dropped into warzones to train local defenders or pro-Imperial elements in order to wage a local insurgency in support of the chapterChapter's own war effort. Other chapters that also employ local insurgencies to their own ends include the [[Alpha Legion]] and [[Word Bearers]].

The Raven Guard are known for their grim and brooding nature. They are thought to be isolationist, dour, and laconic. These traits combined with their preference for secretive and stealth has made them few friends in the wider Imperium.{{Fn|55}} However , due to their history as liberators of slaves, the Raven Guard maintain close ties with mortals, particularly those of their homeworld [[Deliverance]].{{Fn|36a}}

The Rites of Shadow are a Raven Guard and Successor Chapter silent ritual with ancient roots. Conducted in complete silence, Corspake sign language is used for traditional questions and answers. The Rites teach that the shadow contains both trues truth and lies, the purpose of each is the separation of one from the other, and glimpsing of verities otherwise hidden. This is applied to one's Battle-Brother's, one's cause, and even one's foes. Once one has completed the rites, they will earn the status of "Shadow". The title holds great respect, but no rank or authority.{{Fn|36m}}

During the Great Crusade the Raven Guard Legion followed the basic organizational organisational doctrine. The Legion was divided into chapters, chapters were divided into battalions, battalions into companies, and companies into squads. However companies were preferred for most independent operations. Legion officers devolved command responsibility to sub-commanders, allowing them to make tactical decisions and to seek the initiative without interfering with the command chain. The influence of Terran recruits from the Xeric tribes was the cause of this.{{Fn|30a}}

After the Dropsite Massacre, Corax was left with a tattered Legion and had to reorganize reorganise them. They were combined into divisions based on combat specializations. The [[Tactical Squad|tactical companies]] became the '''Talons''', the [[Assault Squad|assault companies]] became the '''Falcons''', and light vehicle squadrons and air support were renamed the '''Hawks'''. Another unit of genetically enhanced Astartes dubbed the [[Raptors (Raven Guard)|Raptors]] were later added as well.{{Fn|30a}}

[[Image:RavenGuardReiver.jpg|thumb|right|300px|Raven Guard [[Reiver]]{{Fn|34a}}]]Owing to the instability of the Raven Guard gene-seed and the experiments of Corax, much of the chapterChapter's genetic stock has been irreparably damaged. Now, much of their genetic material comes from supplies held on [[Terra]]. This means the cycle of recruitment for the Raven Guard is much slower than other Chapters chapters and fewer Raven Guard candidates for the Chapter prove able to survive their training and genetic modification. This means the chapter Chapter is constantly short-handed.{{Fn|2}}

The Raven Guard's chapter planet homeworld [[Deliverance]] is said to lack the population resources available on other chapterchapters's homeworlds. By the time of the Horus Heresy only a few thousand marines in the Raven Guard's number were recruited from Deliverance, the rest made up of the original [[Terra]]n forces inducted before the [[Great Crusade]].{{Fn|1}}

Today, [[Aspirant]]s are considered to be given a high honour of receiving the rare and unstable Gene-seed of the Chapter. They are thus subjected to harsh training in the force-domes of [[Deliverance]] and [[Kiavahr]]. They face lethal conditions with little food, water, or sleep, and are required to evade or kill monsters and [[Mutant]]s and must learn patience, stealth, and the art of the hunt in order to survive. In the Trial of the Watcher, an Aspirant is required to navigate the ganglands of Kiavahr and undertake missions with only the most minimal of visual clues to guide them to their objective.{{Fn|43a}}

In the Trial of Justice, they are tested to see if they can uphold to the ideals of Corax. In this challenge, Aspirants are strapped to a chair in near total darkness and has have their mind examined by Chapter [[Librarian]]s as they are given questions by [[Chaplain]]s on questions relating to loyalty, courage, freedom, and justice. They are often given hypothetical scenarios and complex moral dilemmas and forced to give solutions. There are no true right or wrong answers to these questions, though due to the presence of Librarians an Aspirant can not cannot lie and give responses he knows will please his overseers. A mere attempt at dishonesty sees one killed on the spot or made into a [[Servitor]].{{Fn|43a}}

The Trial of the Wraith is a more physical challenge and forces Aspirants to be dropped alone into the Ologothien Wastes on Kiavahr. They must then traverse 199 miles of lethal territory in three days without sustenance and to be not spotted evade detection by a native predatorpredators. Thus aspirants are forced to utilize utilise their stealth training to the utmost extreme.{{Fn|43a}}

Those that complete their trials can expect long service in the [[10th Company (Raven Guard)|10th Company]] as [[Scout]]s, of which the Raven Guard maintains a higher amount of number compared to other Chapterschapters. Upon proving themselves after years of service in the 10th Company, a full Battle-Brother can take on a new name, often that of a past Chapter champion or a Kiavahran word for a beast, weapons, weapon or folk hero.{{Fn|43a}}

*While stated in the background that all ''Raven Guard'' have black hair, there is at least one instance where [[Games Workshop]] showed a miniature [http://www.games-workshop.com/MEDIA_CustomProductCatalog/m1860548_Raven_guard_AssaultMarines.jpg with a different hair colour] (accessed 2011/09/08){{CME}}. If this is a mistake or deliberate is unknown.