Black Rage

The Black Rage is a psychic curse that afflicts the Blood Angels Chapter and all of their successor Chapters, manifesting as an overwhelming genetic memory of their Primarch Sanguinius's death at the hands of Warmaster Horus during the Siege of Terra. When a Blood Angel succumbs to the Black Rage, he experiences vivid hallucinations, believing himself to be Sanguinius in his final moments aboard the Vengeful Spirit.

This curse is one half of the Blood Angels' dual genetic flaws — the other being the Red Thirst, a vampiric craving for blood. While the Red Thirst can be controlled through discipline and meditation, the Black Rage is irreversible once it takes hold. Affected Marines lose all sense of self, seeing enemies as Horus and allies as fellow defenders of the Emperor.

The Blood Angels have kept this flaw secret from the wider Imperium for millennia, fearing censure or destruction. They manage the afflicted through the Death Company, channeling their madness into one final glorious charge. The Chapter's Sanguinary Priests continually search for a cure, but after ten thousand years, none has been found.