“What wins the fight is what wins the fight. Ultimately, nothing should be excluded if that exclusion leads to defeat.”- Roboute Guilliman
The tale of the Black Hammers begins in dark days of the Horus Heresy, deep beneath the ruined, irradiated surface of the planet Calth. Tor Agamon, a Brother of the 19th Company of the Ultramarines Legion, had survived the Word Bearers' initial act of treachery and joined the other Loyalist survivors beneath the planet's surface as they battled against the hated sons of Lorgar.
Even as Agamon fought, theoreticals tumbled over and over through his mind. The Ultramarine victory had been borne of pure luck, the Word Bearers should have crushed their former brothers. But how had Lorgar's children become so capable, so mighty, that they could so nearly defeat the best trained and most numerous Legion in the Imperium? Brother Agamon had identified only one possible factor; the unknown creatures who seemed to come from the Warp itself. These beings had aided the Word Bearers, given them strength and focus beyond their own reach. Why and how they had done so, Tor had not known, but he was determined to find out. Guilliman himself had taught his Legion; 'Information is victory', so Agamon devoted himself to understanding his enemy. Unbeknownst to his brethren or his superiors, he began to collect and study weapons, armour and other paraphernalia he was able to take from fallen Traitor Marines during Calth's Underground War.
Over the following decades of the Scouring, even as Agamon won honours in battle and promotion through the ranks of the Ultramarines, his obsession with comprehending and negating the power of Chaos continued to grow. By the time the Primarch divided the Legions, Agamon had attained the rank of Master and was given command of 1,000 Ultramarine warriors clad in freshly painted black armour. He named them for his only desire, to hammer to extinction the traitors that cowered within the Eye of Terror. Agamon led his fleet to the Segmentum Obscurus, patrolling the Sectors surrounding the Eye like a coursing hound searching for its prey. For long years the Black Hammers fought against the forces of Chaos wherever they could bring them to battle and Agamon instilled in his warriors a hatred but also a healthy respect for the fell powers of the Great Enemy.
While chasing down a warband of the Emperor's Children, the Black Hammers discovered Gruaimach, a feudal world on the northern edge of the Great Eye. The people of Gruaimach were primitive, grouped into clans and tribes, their fighters warring and raiding against one another to control their home's few resources. However, it was not their aggression or battle skills that made Master Agamon decide to take the world for his own. Rather, it was that he had uncovered on Gruaimach a culture that had somehow found a way to survive despite its close proximity to the raw, ever-warping power of Chaos. The clans fearfully venerated what they called the 'Chinnidh de na Diathan', a terrifying assemblage of divine creatures that Agamon was immediately able to correlate with what he had already learned of the greater Pantheon of Chaos. The Gruaimachii elders had learned to appease and mollify the Gods, turning away their anger with sacrificial offerings and protecting themselves with shamanistic charms and totems. They had come to understand in a limited way the contrary and divided nature of the warp, how one might protect themselves from the fury of one aspect of Chaos by appealing, even temporarily, to its opposite.
Agamon was enthralled by the prospect of learning from the wise men of Gruaimach, of using their knowledge to protect his Chapter and Humanity. Without explaining any of these dangerous thoughts to the Imperial authorities, he claimed the planet as the Black Hammers' own. While initially tight-lipped and unwelcoming towards the giant Astartes, the leaders and shamans of Gruaimach quickly saw the advantage of having such titans as their protectors. They also perceived the eagerness of Master Agamon and his followers to learn of their culture and traditions. In a few scant months, as the Chapter continued in its campaign against the forces of the Traitor Legions, it became commonplace to see Black Hammers Astartes going into battle wearing armour adorned with placatory votive offerings or tokens, or graven with protective charms and warding sigils. At the same time, Chapter Apothecaries had begun to do their work of initiating new brethren from the Gruaimachii clans into the Hammers' Companies, tying the world and its new overlords ever closer.
It was less than half a century later, while fighting in a joint campaign against the vile Death Guard, that the Ultramarines and their Successors would first discover the changes in their Black Hammers brethren. They were horrified by the appearance of the black-clad Astartes, their armour decorated in a manner that seemed to many reminiscent of (and scarcely less disturbing than) the equipment of the Word Bearers at Calth. Tor Agamon and his men were shunned by the other Chapters and, after a blistering argument with the campaign's overall commander, the Black Hammers pulled out and returned to Gruaimach.
Two months later, a punitive force comprised of no less than four full Ultramarines Successor Chapters, led by the Primarch himself, arrived at Gruaimach. Guilliman and his troops were prepared for a bitter siege, their hearts hardened to the possibility of fighting brother Astartes by the long years of the Scouring. What they found was an empty world, devoid of human life but for a few scattered tribespeople. The Black Hammers fortress monastery, it's basic structure only recently completed, had been stripped back almost to the bare foundations. Tor Agamon, ever the strategist, had foreseen what the response of his peers and Primarch must be, as well as the end result of any attempt to stand against them. However, he was unwilling to lose the precious knowledge that could be the salvation of Mankind, simply because of the prejudiced ignorance of others. Therefore he had ordered that his Companies gathered whatever they could, including as many of the Gruaimachii as could be carried in the holds of the Chapter Fleet, and flee.
Gruaimach died that day in the fires of Exterminatus. At the behest of unknown individuals within the Adeptus of Terra, all records of the Black Hammers Chapter were likewise scorched from Imperial history. The scions of Ultramar pursued Agamon's forces across the wilderness between worlds, unrelenting in their hatred for what they saw as a betrayal as great as any of the Heresy. The Black Hammers were hunted from system to system, their beleaguered fleet eventually turning to the only refuge it had left, the Eye of Terror.
One of the Chapters' earliest battles within the Empyrean was to secure a base of operations from which Tor Agamon could continue his research into the mysteries of the Warp. His choice was the Custos Pertinax, a powerful Star Fort, assigned to the World Eaters during the Great Crusade and dragged into the Eye as the Traitor Legions were forced to retreat. However as time passed, few of Khorne's chosen had been willing to accept garrison duty while their brothers rampaged across the stars, leaving the otherwise mighty fortress poorly defended. When the canny Master of the Black Hammers learned this, he quickly threw the entire strength of the newly arrived Chapter against the fortress, overthrowing its remaining occupants in a furious, week-long battle. After this, Agamon took the Custos Pertinax and hid it away in an unimportant star system deep within the Eye. With the aid of his Techmarines he strengthened the Star Fort's Geller Field and Void shield generators. With the aid of the Chapter Librarium and the wise men of Gruaimach he wrapped the vast station about with prayers and spells of warding, misdirection and concealment. With these mystic defences solidly in place, the Black Hammers would have a home from which to continue their work.
Nearly ten millennia have passed since the Black Hammers fled into the Eye. In that time the Chapter has grown strong, moving beyond the strictures of the Codex, and it is estimated that they could muster at least sixteen Companies worth of Astartes warriors, with sufficient fleet assets to deploy them with ease. The Black Hammers Armoury is less impressive, consisting of fewer ground-based fighting vehicles than an 'average' Loyalist Chapter. However the Hammers offset this lack of heavier support with the presence of large numbers of non-Astartes auxiliaries, selected from the former population of Gruaimach. While these clan-born troops cannot compare individually with the Chapter's Marines, they are nevertheless capable soldiers as well trained and equipped as the graduates of any of Ultramar's Battle Academies.
Powerful though the Chapter's resources are, they are minimal when compared with some of the other forces who call the Eye of Terror home, in particular those Traitor Legions who have maintained a central command structure and power base. Therefore, Master Agamon made pacts of mutual support (or at least of non-aggression) with the Black Legion, Iron Warriors and the Thousand Sons, as well as with the Lords of various Dark Mechanicus strongholds. The Black Hammers have ever refused any alliance with the hated Word Bearers Legion, their warriors simply unable to forget the treachery at Calth. Oddly, the scions of Lorgar seem unconcerned by such hatred, rumour even suggesting that the Daemon Primarch himself views the Black Hammers with a certain black amusement, perversely pleased by the thought of the sons of his brother Guilliman turning against their father.
The core beliefs of the Black Hammers Chapter are those of their leader, Tor Agamon. From the earliest days of the Heresy, Agamon believed that the only way for Mankind to be saved from the horrors of the Warp was knowledge. Knowledge of the true nature of the Gods; their strengths, their weaknesses, their goals, their motivations.
Agamon's followers have learned from their Master, though they hide it well from the other denizens of the Eye. The Black Hammers secretly see themselves as Mankind's only true hope for salvation from Chaos. They believe in using the Empyrean, turning its power against itself. Chapter brethren march into battle beneath the icons of Dark Gods, channeling their blessings even as their charms and litanies protect them from the harmful effects of such attention. They also seem to view the colour white as lucky or protective, as many brethren choose to repaint sections of their armour before going into battle, in stark contrast to the black that names them.
The Black Hammers walk a deadly tightrope, as it is all too easy for a warrior to become ensnared by the lure of power that Chaos gives. If a Marine does fall in this way, he will be destroyed without mercy, having become the very thing that the Chapter hates above all else. Remarkably, it seems that the majority of the Black Hammers continue to escape this fate. The Hammers themselves claim that such resilience against the effects of Chaos shows that their ideology is the course of wisdom for all of Mankind. However, an observer with a deeper understanding of the truth of the Empyrean might suggest that no amount of crude charms or litanies can turn away the power of Chaos. They might further imply that the Black Hammers are in reality already lost, protected by some unknown God for its own purposes or caught up in some self-destructive undercurrent within the swirling flows of Chaos.
Despite the Black Hammers turning their backs on the Imperium, their combat doctrine has continued to follow the pragmatic and adaptable combined arms approach espoused by their gene-father. The Chapter's forces tend towards flexible units of infantry, well equipped to face a multitude of different targets. These units work together as precisely coordinated, mutually supporting battle groups, equally able to defend or advance as needed. A handful of vehicles, most typically basic Predators and Dreadnoughts, will provide heavier firepower and units of Gruaimachii clansmen act as light auxiliaries and scouts.
The Chapter often targets other smaller chaotic or renegade forces. This is seen as nothing unusual by the powers-that-be, as warbands all too frequently attack one another for control of resources or to honour their patrons. The Hammers also raid into real-space, ravaging Imperial worlds along the borders of the Eye. Sometimes these are genuine missions to secure needed supplies, sometimes their brutal violence is simply part of maintaining their appearance as devout Chaos worshippers or fulfilling pacts made with other forces. However, on occasion the Chapter is able to use these raids to attack their true enemy. In more instances than can be considered a coincidence, the Black Hammers have decimated a seemingly loyal world, only for Imperial authorities to discover in the aftermath that the planet in question had become the home of Chaos cults, in many cases on the verge of open rebellion.
The geneseed of the Black Hammers is that of Roboute Guilliman. In the few cases that bodies of Marines of the Chapter have been examined by the Adeptus Biologis, these remains have displayed a remarkable lack of the mutation and warping so typically seen among the Traitor Legions. Whether this is due to the absolute purity of the Ultramarines' genetic material, the successful protection of the Black Hammers ritual offerings and charms, or even the blessing of some unknown Chaotic benefactor, is unclear.
A further benefit of this lack of mutation in the Black Hammers genetic material is that their rate of successful geneseed implantation is far, far higher than that of most chaotic warbands. This means that it has been easier for the Chapter to maintain and even incrementally increase its numbers over the millennia, despite the battlefield losses that are common to all renegade forces.
The Black Hammers have no specific war cry, but will often march into battle mumbling Gruaimachii prayer-chants that either request the aid of the Gods or attempt to deflect their notice.