The 4th Black Crusade, also known as the El'Phanor War, was launched into Imperial space from the Eye of Terror by Abaddon the Despoiler in 001.M34, his Black Legion besieging the great Citadel of the Kromarch on the world of El'Phanor.
In an orgy of violence, the Traitor Legions and their daemonic allies fall upon the Kromarch, the Imperial Commander of El'Phanor and his kin, extinguishing their ancient line forever and weakening the defences of the Cadian Gate for future Chaos assaults.
The world of El'Phanor was a stronghold of the Cadian Gate and a key defence against Chaos raiders trying to slip out of the Eye of Terror into the Segmentum Obscurus. Commanded by the Planetary Governor known as the Kromarch, it had repelled countless attacks by the Forces of Chaos in the centuries since the Horus Heresy.
Central to the defences of El'Phanor was the Grand Citadel of the Kromarch, overlooking the vast fertile flood plains of Arabor. The Black Legion descended upon the world like a plague of darkness, half a dozen warbands of the other Traitor Legions slavering for blood in their wake. The Imperial Guard struck repeatedly at the attackers, their assaults supported by massed artillery from the citadel that remained long beyond the reach of the Traitor Legionaries. During this 4th Black Crusade Abaddon personally led the charge against the citadel's adamantium gates through a storm of Heavy Bolter rounds and exploding artillery shells. Only a fraction of the Bringers of Despair, Abaddon's Terminator-armoured elite personal bodyguards, made it to the gates, the great obsidian road to the fortress littered with bloodied and broken Black Legionaries.
Trapped before the gate of the citadel, the Traitors hammered against its mighty doors even as the Imperial Guardsmen swept their ranks with fire from above. Raising Drach'nyen over his head Abaddon struck the gate and the Daemon Weapon split it like cordwood. With the gate sundered, Abaddon and his followers spilled into the fortress, butchering and dismembering all before them.
Abaddon himself took the head of the Kromarch, tearing it from his shoulders in a bloody shower of gore before holding it aloft in triumph. Summoned by the nexus of death within the fortress and this final sacrifice, hungering daemons ripped free of the Warp and added to the pandemonium.
When the last Imperial soldier was hacked apart, the forces of Chaos fell upon themselves, lost in the joy of slaughter. Daemons and Traitors feasted on the ravaged flesh of El'Phanor until it was a dead, wasted planet, and the Fortress World of Cadia was left with a chink in its armour.
- Black Legion: A Codex Chaos Space Marine Supplement (Digital Edition), pg. 33
- Codex: Chaos Space Marines (3rd Edition, 1st Codex), pg. 22
- Codex: Chaos (2nd Edition), pg. 98
- Liber Chaotica: Khorne, pg. 84