The Blood Ravens are a mysterious chapter of Space Marines in the Warhammer 40,000 universe, whose origins are unknown even to themselves. Originally created for the Dawn of War game, they became Canon Immigrants. They feature in C. S. Goto's Dawn of War trilogy, and Chris Robeson's Dawn of War II. The Blood Ravens are unique amongst the Chapters due to their approach to war. Emulating the real time strategy games from which they originated, the Blood Ravens prefer more calculated strikes, analyzing enemy patterns and attacking weak points as they arise, similar to how RTS players break through their opponents. They also do not hesitate to salvage any wargear they find for their own use, let it be from Imperium or Chaos which had earned them the nickname "Bloody Magpies" among fans.The Chapter also is notable for its large collection of Librarians, having a much higher rate of latent psykers within their ranks than normal chapters, to the point where their Chapter Master was simultaneously the Chief Librarian. This has lead to suspicions regarding their origins, which remain a mystery to all but a select few members of the chapter.
The Blood Ravens are depicted as using the following tropes:
Back-to-Back Badasses: Upon administering the poison to kill a Tyranid Splinter Fleet, the Blood Ravens are surrounded on all sides, and fall back to the temple ruins to hold off the Swarm in a last stand.
The Cavalry: After nearly a month's worth of fighting against the Tyranid onslaught, the 3rd Company performs this trope by deep striking into the heart of the swarm at a critical moment, saving the surviving Blood Ravens from annihilation, and providing the soldiers needed to strike a killing blow against the Hive Fleet.
Combat Pragmatist: The Blood Ravens approach to warfare emulates the tactics used by RTS players. Unlike the Space Wolves or Blood Angels' ferocious charges, Blood Ravens focus on analyzing and targeting weak points in enemy lines, applying pressure where needed to break apart far larger forces with minimal casualties. The best example of this comes from Dawn of War 2, where a Combat Patrol sized unit of chapter veterans was able to hold off a sector wide Tyranid invasion by striking at key targets while a relief force was dispatched.
Culture Clash: In Dawn of War 2, this is discussed by the Administrator of Meridian, who argues that the city planet is far more strict than the wildernesses the player had been exposed to so far.
Dark Secret: The Blood Ravens do not know their founding history, as their records are several thousand years short of other chapters. They constantly seek knowledge about their past, and when they find sources, they are coveted fiercely. Additionally, when facing the Chaos Legions, the traitor marines constantly toy with the Blood Ravens, implying that they know some terrible truth about the chapter.
Their unusual approaches to combat and heretical knowledge, high number of Librarians, and color scheme make them a dead ringer for pre-Heresy Thousand Sons. This would make their Primarch the Daemon Prince Magnus, something their predecessors would have been quite eager to cover up.
Deep Sleep: In Chaos Rising, it is revealed during an excursion to a Space Hulk that several members of the Blood Ravens thought dead in the Chapter records had actually survived aboard the vessel. Azariah Kyras had been left on the ship for years before beind rescued.
Disappeared Dad: Since the Chapter's records only date back to M37, the Blood Ravens have no knowledge of their Primarch or progenitor Legion. Acknowledging this, the Blood Ravens instead revere the Unknown Primarch.
Discontinuity Nod: After the poor reception of Dawn of War: Soulstorm, Relic acknowledged the poor quality of the product by making it the butt of a joke in Dawn of War 2, making fun of Commander Boreale's incompetence. Less humorously, in Chaos Rising Cyrus credits Boreale's incompetence as why he defects to the Black Legion if he turns traitor.
Empathic Weapon: If Tarkus turns out to be the traitor in ''Chaos Rising, then his reasoning has been tainted by The Blighted Bolter, an extremely powerful boltgun that has been manipulating his mind and causing him to become more violent and aggressive.
Gladiator Games: Traditionally, Blood Raven recruits are tested in gladiatorial fights called "Blood Trials" where they compete to see which of them are worthy of becoming neophytes.
Interservice Rivalry: While not a massive one like the one between the Dark Angels and the Space Wolves, the Deathwatch sourcebook, Honour The Chapter presents the Space Wolves and Blood Ravens having a bit of a rivalry as an example of the inter-Chapter tensions that can rise in a Deathwatch Kill Team:
The Space Wolves have a long history of distrusting what they view as sorcery, and the highly psychic Blood Ravens Chapter has drawn their ire on more than one occasion. During the battle of Praximil VIII, the Blood Ravens reliance on Librarian intervention to oust the psyker leader of the renegades entrenched there sent their Space Wolves allies into a fury. The Wolf Lord who fought at their side believed the tactics to be dishonourable and he made this known to the Blood Ravens commander with a well-placed punch.
It Was a Gift: The blood Ravens' armory has a staggering amount of items that were "gifted" to them, especially from First Founding Chapters. Has lead to Memetic Mutation implying that the Blood Ravens are:
Kleptomaniac Hero: In Dawn of War 2, much of their wargear consists of relics of other chapters that they "discovered." This has led to the Fan Nickname "Bloody Magpies". On the other hand, the Blood Ravens have a habit of blessing their own relics in the name of heroes from other chapters, and presenting them as gifts to the chapters in question, so maybe they just think its a fair trade.
Well, they do actually have relics belonging to other chapters, including but not limited to: the Fist of Rogal Dorn, an Inquisitor's bolt pistol, a Doom Eagles' plasma pistol, an Adeptus Custodes' breastplate and what may or may not be Marneus Calgar's bolter.
As you can imagion most of these Chapters are not happy with them, or their "gifts". Most notably Ragnar Blackmane busted with laughter while presented with one telling them to keep it.
Last Stand: Three moments stand out in their history. The first was an utter disaster, when Captain Boreale and half the Chapter were slaughtered at the Chapter Keep in the Kaurava System. The second occurred during the Tyranid Invasion, when the remaining Blood Ravens in Subsector Aurelia held off the Tyranid Swarm. The final confrontation took place on Cyrene, where the last surviving loyalist Blood Ravens fought the Daemon of the Maledictum and cleansed Aurelia of Chaos once and for all.
Mysterious Past: The Blood Ravens' chapter records only go back to M37 (the 37th millennium) and they canonically do not know who the identity of their Primarch and parent Legion. Their motto, "Knowledge is power. Guard it well", reflects this. Recent hints during the Horus Heresy series indicate that the Blood Ravens are descendants of one of the traitor legions. The current fan favorite is the Thousand Sons due to the Blood Ravens' high psychic potential and that the Pre-Heresy colour scheme of the Thousand Sons is very similar to the Blood Raven's current scheme. Not to mention that the Corvidae (Latin for Raven), one of the Thousand Sons's cult disciplines, has a raven as it's emblem
Nice Job Breaking It, Hero: The daemon that Gabriel Angelos released in the first Dawn of War later ends up empowering Chapter Master Azariah Kyras' ascension to Daemon Prince.
Not So Different: During his battle with the Blood Ravens on Kronus, Eliphas The Inheritor constantly toys with Captain Thule, teasing him with the notion that the Blood Ravens are closer "brothers" with the Chaos Marines than they realize.
The Other Darrin: All the returning Blood Raven characters got new voices in DOW 2. This was written into the fluff as a chapter-wide genetic anomaly that causes their voices to change every few years.