Men of Stone
"Because Man could not bear the cold of the ocean deeps, he fashioned Men of Stone to go in his place"
- – Kron, Man of Stone. M41
The Men of Stone were a race of humanity created during the earliest stages of their first galactic expansion. Unlike the Men of Gold, the Men of Stone were weaker in body, lacked a philosophical disposition, but were far better artificers and engineers (aka they were the NEEEERRRDDDDDSSSSS of humanity). Being so (relatively) early in humanity's history, little is known of these beings. They were basically the 1.0 version of the Mechanicus of Mars.
The Journal of Keeper Cripias
The Journal of Keeper Cripias is the first mention of the Men of Stone:
"...In time, the Second Men of the Stone Race appear, and in their wake come many miracles and marvels of technology that strengthen the Stone Men’s power, but are also harnessed by those of the Golden Race. Although physically inferior to the Golden Race, and not of philosophical temperament and disposition, the Stone Men have in them the conjurations of great artifices and mechanisms. In time, the Golden Race looks to the stars to expand their dominion. The Stone Race builds great machines of power that send both Men of Stone and Men of Gold into the Ether. However, once the burgeoning race of Mankind has taken its first steps into the greater cosmos, the Golden Race dwindles in influence through their dependence on the artifices of the Stone Race. This the Golden Age comes to an end and the Stone Men prevail.
Our calculations, from the most distant and archaic records, and through constellar comparison, have dated the end of the Golden Age at 20.000 years previous to our present time.
For the next 5.000 years, the Stone Race lives through the Dark Age of Technology. Little can be determined from the Dark Age of Technology, for the majority of existing records concerning that period are gathered in the Librarius Omnis of Mars, and none outside the highest ranks of the Adeptus Mechanicus can gain access past its most determined Guardians (Keeper Malrubius tried once, but to no avail. We have surmised that during the Dark Age of Technology, the Men of Stone created the Iron Men to help them in the building of their Great Empire. At first, the Iron Men are as servants, willing to do the bidding of their masters with no thoughts.
However, the Iron Men, as all creatures do, evolve and grow until they are the equal of the Stone Race and beside each other they set about conquering the galaxy. The Dark Age of Technology is an era of machines and artificial devices, used by the Stone Men, and later the Iron Men, in their endeavours. Many of the technical marvels that the Priesthood of Mars sustain can be traced to their origins in the Dark Age of Technology, and it is at the end of this period that the great organisation now known as the Adeptus Mechanicus was founded. During the Dark Age of Technology, the austere ancestors of the Imperium’s Navis Nobilite are born, and through their unique prowess, mankind forges through the stars. Weapons of great destruction cow the aggression of alien enemies, pushing back the frontiers of Mankind’s dominions.
The end of the Dark Age of Technology is the most obscure region in mankind’s evolutionary tale. For whatever reasons and differences in ideology, the Stone Men and the Iron Men fell to warring with each other. The Iron Men are possessed of no Soul, an anathema to any true Man. The Stone Men in their final acts of self-preservation, annihilated the Iron Men who have turned from ally to foe..."
Kron's story
In the short story "Ancient Histories", a shipman working aboard the Imperial Navy Cruiser, Retribution, tells a story to a greenhorn recently press-ganged aboard the ship. In it, he focuses a bit more and sheds some more light on the Men of Stone.
"'But in time food and water and air ran short on Man's island and he looked to the far islands again. Because he could not bear the cold of the ocean deeps, he fashioned Men of Stone to go in his place, and the Stone Men fashioned Men of Steel to become their hands and eyes. And the Stone Men went forth with their servants and swam in the deep oceans. They found many strange things on the far islands, but none as strange or as wicked as the things that swam in the depths between them; ancient, hungry things older than Man himself. 'But these beasts of the deep hungered for the true life of Man, not the half-life of Stone, so the Stone Men swam unmolested. At first all was well and the Men of Stone planted Man's Seed on many islands, and in time Man learned to travel the oceans himself, hiding in Stone ships to keep out the cold and the hunger of the beasts. All was well and Men spread to many islands far across the ocean, such that some even forgot how they came to be there and that they ever came from just one island at all.’ Kron's tale wound on, telling of how the stone men became estranged from humanity by their journeys through the void. This led to a time of strife when the Men of Steel turned against their stone masters and mankind was riven asunder by wars. A thousand worlds were scoured by the ancient, terrible weapons of those days before the Men of Stone were overthrown, and a million more burned as flesh fought against steel."
What exactly are the Men of Stone?
The basics of what is told of the Men of Stone is that they were an artificially created race of humanity, purpose built to lead humanity's first colonization of other worlds. Given Kron's description, they were somehow unappealing to the daemons of the Warp, so could more safely travel through it.
If characters like Kron are anything to go by, the Men of Stone are a cross between organic human and A.I., sort of like a full A.I. servitor. The bionics house the A.I., which represses the consciousness of the organic body its attached to, while taking full control of his body. This repression of the human's consciousness would also prevent the person from experience emotions or thoughts, likely accounting for why warp entities had little interest in them. The "half life" of the Men of Stone likely referring to how the body of a Man of Stone has a soul, but the soul was made completely dormant and suppressed by the A.I. of the bionics.
It was in all likelihood the Men of Stone who created most of the Dark Age of Technology tech. Such as: the first Warp capable void-ships, warp-drives, and the STC systems. And, of course, they created the Men of Iron.
Essentially, the Men of Stone are like prototype, mobile STC, sapient, A.I. servitors.
Likely Men of Stone
Kron
During the events of the short story "Ancient Histories", the character named "Kron" is made apparent to be one of these "Men of Stone". Kron is an old shipman who has had half his skull replaced with cybernetics, including a glowing red eye (that is made out to give HEAVY HAL 9000 vibes). While fighting off a Mechanicus ambush aboard his ship, he is knocked out cold, and his bionics are knocked off line. When he comes too, he is obviously not the same person shown before. Completely confused about his surroundings, his voice completely changed, he starts to panic and begs his shipmate Nathan to get the cybernetics off of him, while trying to pull them off. Nathan stops him, confused as all bloody hell as to what is going on. Kron's bionics then come back online and he is back to acting like nothing was wrong.
Later, while talking with Nathan, he gives the history of the ship, saying how it got stuck in a space hulk for 2,000 years, before being recovered by the Imperium and returned to service for abother 1,800 years. He ALMOST lets it slip that he had been with the ship that whole time, before managing to shut himself up. Later still, he managed survive getting hit square in the chest by a Chaos Space Marine's bolt pistol round, blowing his chest wide open. Not only did he survive, but he killed the bastard by firing a blast of lightning, like a Electro Priest (thought when Nathan calls him one, he outright denies that he is anything of the sort. Its likely that Kron salvaged the Electro-Priest's electoos and installed them into himself). He then rescued Nathan by giving him his void-suit's helmet (as the chamber had become depressurized), which should have seen him suffocate. Though when Nathan wakes up, he finds Kron had patch up his wounded arm (which got shredded by a chainsword) and given him a bionic eye to replace his organic one that had been popped when the Chaos Marine pistol-whipped the fuck outta him. The new eye had PERFECT vision, something that is rarely-to-never seen in 40k augmetics, and Kron had apparently made it for him, from scrap laying around, in only a matter of 5 hours.
Olamic Quietude
The Olamic Quietude were a civilization of humans who are implanted with bionics from birth which linked them together to a social network (so like Facebook, but you can't log off). They would cyberize themselves to the point of leaving very little organic matter remaining. They also considered the Imperium as a bunch of xeno-tainted mutants, while they themselves were the true humans. If they were Men of Stone, then they wouldn't be wrong or lying.
House Van Saar
This noble house from Necromunda has its origins in the survivors of a Dark Age colony ship that was lost in the warp and crashed upon Necromunda in M35. The ship was called the Van Saar (where the house gets its name). Even in modern 40k, House Van Saar has retained its relatively fresh knowledge of technology.
Leagues of Votann
With the recent reveal that the Squats originated from generation ships of humans with AI cores that emerged from being genetically engineered as a race of modified clones that are altered every generation to the point of being specialized in void adaptivity and altered warp signature to hide from warp predation, it seems that spce dorfs might fit the Stone archetype down to the capital S.