Cult of the Red Heresy

The Cult of the Red Heresy was an anti-Imperial Human anarchist movement and Chaos Cult active during the 36th Millennium, from 290-310.M36.

Aided by the Fallen Angel Cypher, they gained support from seven different star systems in the Don'lorth Sector.

However, in the midst of the Plague of Unbelief, Cypher betrayed the cult and helped the Silver Skulls Chapter suppress its rebellion. It is unknown why Cypher first aided, and then betrayed the cult.

History
During the Age of Apostasy, in 290.M36, the Red Heresy Plague erupted across the Don'lorth Sector, a foreshadowing of the later battles that would become known as the Plague of Unbelief. It is here that the Cult of the Old Gods rises.

Agitators and anarchists stirred up the hive cities into open rebellion. Workers in their untold billions were urged by red-robed priests to cast off their shackles, to reject the Corpse God that was the Emperor. The horrific slaughter of all agents of the Adeptus Administratum and Adeptus Ministorum was enough to draw in vast fleets of Imperial armed forces.

Seeking a quick way to end the rebellion, the Silver Skulls Chapter deployed en masse in a desperate attempt to kill the leaders behind the rising cult. The hunt proved disastrous -- with Drop Pod assaults ambushed and multiple Thunderhawks brought down en route to their objectives.

Only the arrival of Dark Angels Deathwing and Ravenwing forces, along with the 3rd Company of the Angels of Vengeance, staved off certain defeat. However, the Silver Skulls observed the Deathwing forsaking the battle in pursuit of a mysterious robed Space Marine, who turns out to be the notorious Fallen known as Cypher.

Before Cypher escaped, an Angels of Vengeance Librarian detected several Fallen Angels ensconced within the red-robed hierarchy of the Red Heresy.

The Silver Skulls were left to dig themselves out of their own predicament. They did so, but openly condemned the Dark Angels; another formal protest about their behaviour was filed with the High Lords of Terra.