Techno Dominion

Originating from the Hive/Industrial World of Eisen in Segmentum Ultima, the Eisen Armed Forces are an Imperial Guard force well known for their high number of weapons, armor and vehicles, many of them found only in their regiments. Along with their impressive armoury, the soldiers of the regiments are famous for their indomitable wills in the face of their foes, and strong bonds of comradeship one would normally see from the Adeptus Astartes. They are also known to have strong relations with the Adeptus Mechanicus.

History
In official Imperial Records, the planet Eisen was discovered by Imperial Forces in the 32nd Millennium, after the Horus Heresy, and believed to have been either an Imperial Planet that had somehow escaped the horrors of the Civil War, or was founded before the birth of the Imperium. The population had already advanced and built multiple cities, as well as possessing some capabilities of space travel. However the truth was much more complicated than that.

Origins
The people of Eisen are in fact descendants of the survivors from the Auretian Technocracy, a once technologically-advanced and peaceful independent human civilization scattered across several star system in the Galaxy. The Technocracy had been conquered and destroyed by the Primarch Horus Lupercal, already under the sway of Chaos, who had desired the several STCs under the Technocracy's possession, in order to gain the Adeptus Mechanicus's allegiance. The survivors, led by the sole remaining member of the Technocracy's elite force, The Brotherhood, Xander Jaquie, towards Eisen, having taken what STCs and other items of importance he could gather.

Even before the tragedy, Eisen was already being colonized by the Auretian Technocracy fifteen years before the coming of Horus, with a few settlements already built. Thus, the planet had escaped unnoticed by the Warmaster, who had already acquired the STCs he needed. So the remnants of the Technocracy were able to remain hidden from the dreadful civil war that came after, and slowly rebuild their home.