- "What are the Keys of Hel? They are the fires taken from the mountain. They are what should not and must not be. Only in the last days of humanity, when law has no meaning, should any think to break the locks placed upon them. These are those days."
The Keys of Hel were the seals placed upon forbidden technological knowledge by Ferrus Manus, Primarch of the Iron Hands Space Marine Legion during the Great Crusade era of the late 30th Millennium. These included the true rites of cybernetic resurrection from death. Where such elements of forbidden technology or lore were encountered (and indeed recognised for what they were only by the Iron Hands), they were seized and suppressed by the Primarch's express order and withheld, it was rumoured, even from the Mechanicum. Few outside the X Legion knew of the ban placed by Ferrus Manus on such forbidden technology as the Sarcosan Formulae, the Progression of the Seventh Gate, and the Ophidian Scale. Even amongst his sons few knew more than the name and, of those who did know, most grasped only the shadows of dark possibility.
Cyber-resurrection, ghola, death and life bound by field, woven by metal or sung by axioms of the unknown -- the names for forbidden technologies across the galaxy were legion. Created by man in the Dark Age of Technology, or by alien hands under cruel suns, their origin does not matter. They were the evolution of Mankind that Ferrus Manus had placed beyond his Astartes' reach, the lock upon a gate to a denied realm. But after the death of Ferrus Manus at the hands of his Chaos-corrupted brother Primarch Fulgrim of the Emperor's Children at the Drop Site Massacre on Istvaan V, some of the Iron Hands who survived the slaughter went mad with grief. They resorted to the use of these forbidden technologies and "turned the Keys of Hel," seeking out any advantage they could utilise against the Traitor Legions to exact their righteous vengeance for the loss of their gene-father.
- "The true danger of the unknown lies not in its existence, but in knowing that it exists."
During the latter years of the Great Crusade the Iron Hands Legion's obsession with strength and the elimination of physical and mental weakness led them to revere the machine and distrust the failings inherent in flesh. While other Space Marine Legions were bound in metal and laboured to create great machines of war, for the Iron Hands, inculcated in their own idiosyncratic beliefs inherited from the Cult Mechanicus' influence on their homeworld of Medusa, the machine was not merely an appendage to flesh but its inheritor. To them their Emperor-augmented transhuman bodies were neither more nor less than a living machine of blood and gristle made for war, a machine which could be repaired and improved upon as opportunity allowed and need commanded.
To be as strong as iron was the fire that drove the Iron Hands, and to speed recovery times cybernetic replacements, swifter by far to employ than the genetic regeneration and vat-grown transplant techniques commonly used by the Legiones Astartes, were favoured, and were capable of getting a fallen or severely injured Astartes back into the fight with frightening speed. As a result, no Iron Hands Legionary who had served in battle for any length of time was wholly without bionic augmentation, and such implants were marks of honour, and often improved and augmented away from the battle's pressing need. Some of the most veteran among the Iron Hands went so far that they were little more than machines cradling shreds of their former humanity. So it was with them that to be interred within a Dreadnought body and therefore allowed to fight for their Primarch and the great cause of unifying humanity forever, was the highest honour any member of the X Legion could aspire to.
But there were limits to what even Ferrus Manus would countenance and, while he lived, certain mysteries of cybermancy such as the true rites of cybernetic resurrection from death remained proscribed as nightmare sciences of the Dark Age of Technology. Where such elements of them were encountered by the Iron Hands Legion during the Great Crusade (and indeed alone among the Legions they could easily recognise them for what they were), they were seized and suppressed by the Primarch's express order and withheld, it was rumoured, even from the Mechanicum. Whispers remained of such horrors as the Agesine Protocols, the Eight Sleepers, and the damned Sarcosan Formulae; all remained locked under the covenants of the so-called Keys of Hel, named for the mythic goddess of the Medusan pantheon. Kept deep within the vaults of Medusa and sunk in chambers on airless rocks orbiting lifeless star systems where none save a select few of the Iron Fathers of the X Legion knew of their location, they were put beyond reach but not destroyed. After the death of Ferrus Manus, however, some saw his resistance to a wider supplanting of flesh with steel as one of the flaws that had allowed him to be destroyed by the Traitors; for the impetuous rage that led him to his death was born of flesh and that flesh had failed him. Thereafter, in the dark times that followed, some among the Iron Hands saw virtue in what had once been forbidden and, it is said, turned the Keys of Hel -- and opened the path to heretekal damnation.
- The Horus Heresy - Book Two: Massacre (Forge World Series) by Alan Bligh, pg. 91
- Riven (Short Story) by John French
- Meduson (Anthology), "The Keys of Hel" by John French
- Sons of the Forge (Novella) by Nick Kyme