|This article is about the Crusades of the Chaos Space Marines, for the RPG serie see Black Crusade (RPG series)|
A Black Crusade is an incursion that is formed when the usually disparate forces of Chaos unite under a particularly strong Chaos Champion and go forth en masse to wage war against the Imperium of Man.
Following the devastating events of the Horus Heresy, the Imperium began the Great Scouring, a campaign to cast out all traitors who had sided with Chaos and drove them into the warp storm known as the Eye of Terror. There, the followers of Chaos began to fight among each other for domination and territory and their vast armies eventually fractured.
Even so, the threat the exiles posed was far from gone. To this day they seek to overthrow the Imperium, launching separate raids and invasions against it. Once or twice within a millennium however, an exceptional Chaos Champion rises who is strong enough to bring his fellow warlords and their hosts under his sway. When this happens ancient rivalries are set aside and uneasy alliances are forged, clearing the way for what is called a Black Crusade.  
The forces and fleets that gather for a Black Crusade are made up of all types of Chaos servants: the multitudinous hordes of the Lost and the Damned, ancient and towering Chaos Titans, the bizarre war machines of the Dark Mechanicum and the Daemons of the warp. Leading them into the realm of man are the vengeful warbands of the Chaos Space Marines. 
When the crusade is launched, whole worlds fall prey to the rampaging hordes and the Dark Gods themselves divert their attention to the material realm, delighting in the sacrifices made in their names. Still, the nature of Chaos is fickle and unless it is repelled by the defenders, the crusade is bound to splinter into separate hosts and warbands who pursue their own ambitions.
The Black Crusades of Abaddon the Despoiler
The most infamous Black Crusades are those led by Abaddon the Despoiler, Warmaster of the Black Legion and successor to Horus. So far, he has led thirteen such attacks, which ranged from small raids to battles that spanned entire sectors. His latest Black Crusade, the Thirteenth, has succeeded in destroying Cadia.
The Black Crusaders of Abaddon have a secret and even more sinister purpose. Throughout the Millennia he has identified ancient monoliths holding back the tides of the Warp. Using his Black Crusades to sometimes conceal his true objective, Abaddon has targeted and destroyed many of these structures as part of a plan known as the Crimson Path. The ultimate objective of Abaddon's Black Crusades is to expand the Eye of Terror to envelop Terra itself.
- 781.M31 - 1st Black Crusade, The First Battle of Cadia. Abaddon claims the daemon sword Drach'nyen.[8a]
- 597.M32 - 2nd Black Crusade, the Cursing of Corona. Abaddon invokes a curse that sinks into the core of Belis Corona.[8a]
- 909.M32 - 3rd Black Crusade, the Host of Tallomin, Desecration of Gerstahl. Abaddon destroys the remains of Saint Gerstahl.[8a]
- 001.M34 - 4th Black Crusade, the Devastation of El'Phanor, the Death of the Kromarch. Destruction of the Grand Citadel of Kromarch.[8a]
- 723.M36 - 5th Black Crusade, the Tide of Blood, the Scouring of Elysia. Abaddon summons the daemon prince Doombreed and destroys the Warhawks and Venerators Chapters.[8a]
- 901.M36 - 6th Black Crusade, Drecarth's Folly. Abaddon brings the Sons of the Eye to heel.[8a]
- 811.M37 - 7th Black Crusade, the Ghost War. Abaddon claims the gene-seed of Blood Angels slaughtered at Mackan.[8a]
- 999.M37 - 8th Black Crusade, the Skullgather. Abaddon appeases the Changer of Ways with sequences of death creating a mathematical equation of terrible and profane perfection.[8a]
- 573.M38 - 9th Black Crusade, the Starving of Cancephalus. Several Chaos fleets leave the Eye of Terror undetected during the Antecanis Massacre.[8a]
- 001.M39 - 10th Black Crusade, the Conflict of Helica. Abaddon and the Iron Warriors fight the Iron Hands at Medusa.[8a]
- 301.M39 - 11th Black Crusade, the Doom of Relorria. Abaddon abducts thousands of orks to conduct experiments on their use of the warp.[8a]
- 139.M41 - 12th Black Crusade, the Gothic War. Abaddon captures the last two Blackstone Fortresses.[8b]
- 999.M41 - 13th Black Crusade, the Fall of Cadia. Abaddon gathers the blessings of the Daemon Primarchs and launches a major attack on the Cadian system (currently ongoing).[8c]
Other known Black Crusades
- c.034.M31 - The Primarch of the Imperial Fists, Rogal Dorn, was killed while stopping a Black Crusade by an unknown force sometime after the Horus Heresy
- M34 - The Blackstar Crusade. Lord Ekrak, a champion of Khorne, leads a crusade to conquer the world of M'Laar XIII and ascends to deamonhood.
- M36 - The Black Crusade of Sicklefell. A century long war saw the Forge World Barnassus destroyed and thirty-three worlds systematically murdered.
- 599.M37 - The Black Crusade of Jihar the Lacerator. Jihar the Lacerator, champion of Slaanesh, inspires uprisings on the Gloom Worlds before an unexpectedly sudden defeat.
- Between 113.M38 and 955.M39 - The Black Crusade of Von Mallas. Lord Von Mallas reduces the Agri-World Epirus to a wasteland, causing famine throughout the sector.
- Pre-997.M41 - The Black Crusade of Furion. Khornate Lord Furion of the Skull-Scythes attacks the Dark Angels, killing Master Nedael.
- The Black Crusade of the Destroyer. The Destroyer, a daemon of Tzeentch, possesses Captain Leonatas of the Blood Angels.
- 1: Liber Chaotica: Khorne, Black Crusades
- 2: Codex: Eye of Terror, pg. 9
- 3: Tactica Imperialis, [Needs Citation]
- 4: Warhammer 40,000 4th Edition Rulebook, pg. 136
- 5: Codex: Chaos Space Marines (4th Edition), pgs. 24, 46
- 6: White Dwarf 246 (US), "The Powers That Be" by Jonathan Green
- 7: Index Astartes II - The Emperor's Fists
- 8: Black Legion - A Codex: Chaos Space Marines Supplement
- 9: Codex: Dark Angels (4th Edition), Belial
- 10: Bloodquest (Graphic Novel Series)
- 11: Fire Warrior (Novel), Chapter 5, pgs.135-136
- 12: Imperial Armour Volume Twelve - The Fall of Orpheus, pg.29
- 13: Codex: Chaos Space Marines (8th Edition) pg.16