A Black Crusade is when the Forces of Chaos manage to unite under the leadership of a powerful Champion of Chaos and launch a massive attack from within the Eye of Terror against the worlds of the Imperium of Man. Most of the Black Crusades were led by the Warmaster of the Black Legion, Abaddon the Despoiler, the self-proclaimed heir of Horus, who has led 13 Black Crusades against the Imperium, the most recent of which was the 13th Black Crusade in 999.M41.
The 1st Black Crusade occurred in the middle of the 31st Millennium, not long after the end of the Horus Heresy in 731.M31. Utilizing the region of calm around the Eye of Terror known as the Cadian Gate, Abaddon led the combined forces of the Traitor Legions against scores of Imperial worlds, and was responsible for millions of deaths in the first week alone. Multiple worlds were lost before the Imperium could fight back effectively, and although the Black Crusade was defeated, the Imperium was forced to heavily fortify the surrounding Cadian Sector.
Over the course of the intervening ten thousand standard years, Abaddon has launched a further twelve Black Crusades. Millions of other attacks have been made on the worlds of the Cadian Gate by Daemon Princes and lesser Chaos warlords, but the title of Black Crusade is reserved for the times when Abaddon seems to be able to unite all of the Forces of Chaos in the pursuit of one goal--the destruction of the Imperium of Man, the greatest bastion of Order in the galaxy.
The 41st Millennium saw two Black Crusades. The 12th Black Crusade, also known as the Gothic War, was Abaddon's attempt to capture the ancient Eldar artifacts known as the Talismans of Vaul, but known to the Imperium as the six Blackstone Fortresses. The Eldar allied themselves with the Imperium to defeat the Chaos forces, and were successful, although Abaddon escaped with at least two of the Blackstone Fortresses.
The Thirteenth Black Crusade began during the 999th year of the 41st Millennium, and resulted in the largest mobilisation of both Imperial and Chaotic forces seen since the Horus Heresy. In this campaign, at least one of the Blackstone Fortresses was destroyed by Necron raiders; the fortresses, also known as the Talismans of Vaul by the Eldar, were originally designed to defeat the "Star Gods" - the C'tan, during the ancient War in heaven between the C'tan's Necron servants and the Old Ones.
The Thirteenth Black Crusade was the background to the world-wide Eye of Terror campaign, which resulted in a minor victory for the forces of Chaos and gave Abaddon a foothold on the Cadian Gate, though he suffered devastating losses to his fleet. Admiral Quarren led a counter-attack that drove off Abaddon's Chaos-corrupted Blackstone Fortress, but Abaddon's foothold on the Gate remains with fighting still ongoing on Cadia and the surrounding worlds. In response, the Imperium has stripped garrisons along its far Eastern Fringe to reinforce the Cadian Gate, which resulted in a full retreat of the forces of Chaos from the Cadian Gate, resulting in a current stalemate. However, this weakening of Imperial defences hastened the onslaught of the Tyranid Hive Fleet Leviathan.
List of Black Crusades
- The First Black Crusade - circa 781.M31 - The First Battle of Cadia. (Codex: Chaos Space Marines 3rd edition)
- The Second Black Crusade - 597.M32 - Failed attack on defences of Cadia. (Liber Chaotica: Khorne)
- The Third Black Crusade - 909.M32 - The Host of Tallomine. Daemon Prince Tallomin leads attack that is crushed by the Space Wolves. (Liber Chaotica: Khorne)
- The Fourth Black Crusade - circa 001.M34 - Abaddon's forces succeed at carrying out the destruction of the Citadel of Kromarch on the world of El'Phanor before the Forces of Chaos are crushed once more by the Imperium's stalwart defenders. (Liber Chaotica: Khorne)
- The Fifth Black Crusade - 723.M36 - Doombreed, a Daemon Prince of Khorne, declares war on the Adeptus Astartes. The Warhawks and the Venerators Chapters of Space Marines are lost in the fighting. (Liber Chaotica: Khorne)
- The Sixth Black Crusade - 901.M36 - No information about this conflict is currently known.
- The Seventh Black Crusade - 811.M37 - The Seventh Black Crusade is also known in Imperial records as the Ghost War (Liber Chaotica: Khorne). It is during this conflict that the Forces of Chaos slaughter a large portion of the Blood Angels Chapter of Space Marines at the Battle of Mackan (Codex: Chaos Space Marines 3rd edition).
- The Eighth Black Crusade - 999.M37 - No information about this conflict is currently known.
- The Ninth Black Crusade - 537.M38 - No information about this conflict is currently known.
- The Tenth Black Crusade - 001.M39 The Conflict of Helica. Iron Warriors fight Iron Hands at Medusa. (Liber Chaotica: Khorne)
- The Eleventh Black Crusade - 301.M39 No information about this conflict is currently known.
- The Twelfth Black Crusade - 139.M41 - Better known as the Gothic War, this Black Crusade was fought for control of the Gothic Sector in the Segmentum Obscurus between the Chaos forces of Abaddon the Despoiler and the defenders of the Imperium (Liber Chaotica: Khorne, Battlefleet Gothic).
- The Thirteenth Black Crusade - 999.M41 - The Chaos Champion Abaddon the Despoiler launches an all-out attack of the forces of Chaos Undivided on Cadia. (Codex: Eye of Terror)
- Codex: Chaos Space Marines (3rd Edition)
- Liber Chaotica: Khorne
- Codex: Eye of Terror
- Battlefleet Gothic: The Galaxy