The Blood Angels and their Successor Chapters of Loyalist Space Marines still suffer from a genetic flaw that creates mental instability called the Black Rage, also known as the Flaw of Sanguinius, as a result of the psychic imprint left by their Primarch Sanguinius' death (or by the terrible wound given to Sanguinius on Signus Prime by the Bloodthirster Greater Daemon Ka'Bandha) at the hands of Horus. This can cause them to go insane prior to or during battle and feel the rage of Sanguinius himself during the final days of the Battle of Terra. The condition is largely irrecoverable and only a few Blood Angels have managed to defeat the "Gene Curse". Victims are locked away in the Tower of Amareo (named after an ancient Chapter Master of the Blood Angels), also called the Tower of the Lost, on the Blood Angels' homeworld of Baal.
When a Space Marine is overcome by the Black Rage he is reborn into a world of constant anger, hatred, fury and nothing else. As well as Sanguinius' memories, the Blood Angels and their kin are genetically touched with a small portion of the Primarch's unearthly power, boosting their strength and vitality to superhuman levels. Rather than let them face a slow, insane death, Blood Angels and their Successors will form those Battle-Brothers who have newly succumbed to the Black Rage into a special unit of the Chapter known as the Death Company. They wear specially painted black Power Armour, daubed with red crosses to symbolise the wounds of Sanguinius and are often led by the few Chapter officers, notably Chaplains, who are able to communicate orders to the insane troops. They are then sent out to perform the most dangerous assaults, hoping for a quick and honourable death in combat.
However, by some unknown means, the genetic flaw in the Blood Angels' gene-seed that produces the Black Rage also seems capable of extending the victim's lifespan, at least until he finally succumbs to the Rage. Lord Commander Dante, the Chapter Master of the Blood Angels, is by far the oldest living Loyalist Space Marine (not including those interred in a Dreadnought), born more than 1000 Terran years before the present time, a feat that may only have been possible because of the genetic flaw he bears.
Blood Angels Freed From the Flaw
- Lord Mephiston - Originally Battle-Brother Calistarius, a Blood Angels Librarian of some considerable ability and strength of character, Calistarius was almost overcome by the Curse of the Black Rage when he served as part of the relief force for Hades Hive during the Second War for Armageddon, where, having suffered for 7 days and nights trapped in the rubble of the collapsed Ecclesorium building, a vision of Sanguinius helped him fight off the effects. He was reborn as Mephiston – the Lord of Death, and with his full psychic potential unlocked, quickly achieved the position of Chief Librarian for the Blood Angels Chapter. He is seen as the spiritual son of Sanguinius, a figure of hope to his Chapter. He is now considered to be the most powerful Librarian in the Adeptus Astartes, and possibly the most powerful psyker in the Imperium, after the Emperor of Mankind.
- Sergeant Rafen - A Battle-Brother -- later promoted to Sergeant -- he had to kill his brother Arkio who was claiming to be Sanguinius reborn but was in reality deceived by Chaos, having been made, through mutation, into a likeness of Sanguinius. Rafen then had to succumb to the Gene Curse to unleash the power of the Holy Spear of Telesto (a weapon wielded by Sanguinius himself) in order to defeat Malfallax, a Lord of Change (a Greater Daemon of Tzeentch) who had deceived Arkio. However, he was eventually able to pull himself to the surface of his consciousness, and also succeeded in helping Mephiston defeat the Black Rage within himself a second time. Rafen was the protagonist of the Blood Angels series of novels by James Swallow.
- Codex: Blood Angels (5th Edition)
- Imperial Armour Volume Two - Second Edition: War Machines of the Adeptus Astartes, pg. 167
- Index Astartes I, "Blood Frenzy - The Flesh Tearers Space Marine Chapter"
- Index Astartes II, "Angels of Death - The Blood Angels Space Marine Chapter", pp. 34-37