The Ironclad Brotherhood, known formally as the Frateris Firmitatis, is a collective formerly made up a quadrumvirate of Second Founding Iron Hands' Successor Chapters of like-mind and temperament - to wage an eternal war against the Traitor Legions and those who would make truck with the Ruinous Powers. Unfortunately, this fraternity was sundered when the formerly loyalist Chapter, the Iron Invictors, let their obsession with certain forbidden mysteries and nightmare sciences of the Dark Age of Technology saw them declared Excommunicate Traitoris, and cast out of the Imperium.
The remaining three loyalist Chapters - the Iron Gorgons, Iron Harbingers and the Templars of Iron - which still make up this triumvirate collective, continues to honour their compact made nine millennia earlier. This fraternity will often gather for common cause or come to one another's aid during times of crisis, and when they have done so, they have achieved great victories and averted several potential disasters throughout the Imperium's long history. Their secondary goal is to seek out their erstwhile former brethren, now known as the notorious Chaos warband, the Brethren of Hel, and to finally eradicate the stain upon their brotherhood's honour once and for all.
The X Legion were created by the Emperor during the dawning of the Great Crusade. They would go on to be forged in fire and war to bring the light of humanity and the Imperial Truth to the long lost human worlds scattered across the galaxy. After they discovered their Primarch Ferrus Manus upon the unforgiving world of Medusa, the X Legion was reforged anew, shaped and tempered into a lethal weapon of their lord's choosing, becoming the unrelenting and bellicose Iron Hands. When the Horus Heresy erupted and plunged the nascent Imperium into total war, the Iron Hands Legion was far from Terra and unable to intervene directly.
Primarch Ferrus Manus was enraged by the weakness of the other Legions, and by his inability to fight the traitors. He gathered together his most veteran troops and departed for the Istvaan System. It was there that the traitor Primarchs, Warmaster Horus first among them, revealed the full extent of their treachery. They ambushed the Iron Hands, the Raven Guard and the Salamanders, and although the three loyal Legions fought valiantly, Ferrus Manus himself was lost. The Iron Hands were undone by their own hubris and the blade of the traitor both, and paid a heavy price in the brutal slaying of their Primarch and the near-crippling of their strength. Though left a shattered Legion, the cold fury of the Iron Hands' bitter vengeance would afterwards be writ across the stars.
Reeling from the monstrous blow dealt to them, the Iron Hands were reduced to a shadow of its former strength. The fractured Iron Hands were drawn together on Medusa for a great conclave known as the Tempering. During this great debate the Iron Hands come to embrace their inherent beliefs in 'iron over flesh' - for it was human frailty which had caused the corruption of the Primarchs and their Legions, as well as those mortals who let their own jealousy, avarice and fear lure them into following the Warmaster into rebellion and eventual damnation.
The Iron Hands vowed to seek out weakness and destroy it, replacing it with machine-like fortitude that they had come to venerate. This great council sets the Legion's feet on a path that it will follow, for better or worse, for the next ten thousand years. The incensent rage stroked by the Iron Hands' fury was fully unleashed upon the Traitor Legions, following their defeat during the Siege of Terra, and their subsequent flight. This war of reciprocity came to be known as the Great Scouring.
Following the events of the Scouring, the dawning of the galaxy-spanning Imperium and the rebirth of the domain of Mankind occurred. Almost immediately following its inception, the newborn Imperium was forced to rise from the ashes of the Horus Heresy. Now shorn of the Emperor's leadership, nearly everything was reorganised and many fail-safes were put into place. Countless doctrines, the most famous of which was the Codex Astartes, the magnum opus of the Ultramarines Primarch Roboute Guilliman, were drawn up and implemented in the hope of ensuring that a large-scale military rebellions was never again possible.
The remaining loyal Space Marine Legions were disbanded to form the far smaller 1,000-man organisations known as Chapters. A portion of the Space Marines maintained their parent Legions' original names, badges and colours while the remaining Chapters took on new names and heraldry. Thus, the Second Founding occurred, and the Iron Hands went on to Found multiple Chapters.
The Iron Hands saw the perfect opportunity to rid themselves of the troublesome elements within their Legion, and so, the Iron Council decreed that certain Clan Companies who had been deemed vexatious, would be granted the 'honour' of becoming new Chapters. Each newly created Iron Hands Successor Chapter took on the traditions and rites of their Progenitor as the basis for their new brotherhood and adopted a fitting name. Stripped of title and tithe, history and deed, these Clan Companies were forced to make their own way in an unforgiving and uncaring galaxy.
Inception of the Frateris Firmitatis
Following their Founding, several of these newly created Iron Hands Successor Chapters found themselves of like-mind and temperament, as well as their propensity for waging an unforgiving war upon the Traitor Legions and other followers of the Ruinous Powers. A great conclave was called between these Scions of Ferrus Manus, and so, the lords of each Chapter sent a delegation and met upon the moon of Hephaestus, located within the Thule Sector. This ancient planet, which had formerly served as an industrial complex and was a part of the Iron Hands' tributary fiefdom, had long ago been abandoned following the Horus Heresy. It was upon this lifeless planetoid that a powerful alliance was formed, known as the 'Ironclad Compact'. Four Iron Hands Successor Chapters, which consisted of the Iron Gorgons, Iron Harbingers, Iron Invictors, and the Templars of Iron, formed a powerful conglomerate, that collectively became known as the Frateris Firmitatis or 'The Ironclad Brotherhood'. These Chapters possessed similarly war-like natures and unforgiving temperaments.
Down the centuries, the Ironclad Brotherhood would often come together in conjunction with one another to work towards a common goal or to vanquish a particularly troublesome or powerful enemy force. As fleet-based Chapters, this alliance of powerful Astartes Chapters saw them travel the length and breadth of the galaxy to enact their brutal retribution upon the heretic, the apostate and the xenos. They achieved numerous victories and the destruction of many terrible foes.
This stalwart alliance remained resolute and inviolable for over a millennium and a half, until it was shattered by the actions of the Iron Invictors, who overstepped their bonds of brotherhood in their obsessive quest for obtaining certain forbidden technology, and opened themselves to the path of heretical damnation. The Iron Invictors were declared Excommunicate Traitoris by Inquisitorial edict. Thus began a series of bloody and bitter battles between the remaining Ironclad Brotherhood Chapters and their erstwhile kin. But the majority of the Renegade Chapter escaped their former brethrens' wrath, and butchered their way through several systems, before finding refuge within the hellish realm known as the Eye of Terror.