The xenos species known as the Ur'Iso were first encountered during the Great Crusade in the Mundi Sector by the 620th Expeditionary Fleet. Accompanied by the 26th Chapter of the Ultramarines legion under the command of Chapter Master Septimus Kyros, the 620th Expeditionary Fleet made some initial headway in the Mundi Sector before stalling as the full extent of the Ur'Iso Ecumene was discovered.
At its height, the Ur'Iso Ecumene was confirmed to hold territory in the Imperial Sectors of Asgardia, Chode, Damocles, Jericho, Lostrix, Mundi, Nurth and Prismur with the Asgardia Sector being the centre of their fledgling empire. The Ur'Iso Ecumene nominally claimed to rightfully own the entire galaxy in a fit of xenos arrogance though the Ur'Iso never came close to fulfilling this outrageous claim.
While the Ur'Iso achieved spaceflight during the Dark Age of Technology, they didn't arise to prominence until the Age of Strife. Taking advantage of mankind's weakness in those dark days, the perfidiously Ur'Iso attacked and conquered several frontier regions of human space now that the human colonies could no longer receive aid from the rest of humanity.
Until the Great Crusade reached them, the Ur'Iso Ecumene had enslaved a multitude of human worlds under their reign. While the Ur'Iso didn't exterminate the local populace, they did reduce them to pre-spacefaring technology and are widely considered the reason for why that region of space has an abnormally high number of feral and feudal worlds.
The Ur'Iso Ecumene ultimately came to an end at the hands of the XIII Legion. After the xenos stemmed the advance of the 620th Expeditionary Fleetin the Mundi Sector and proved themselves to be a technological peer, Chapter Master Septimus Kyros called upon Primarch Roboute Guilliman to provide reinforcements. After assessing the situation, the Primarch personally came to the front with the 12th Expeditionary Fleet and the largest individual concentration of the Ultramarines at the time.
While the 620th Expeditionary Fleet began to suffer heavy losses as the Ur'Iso sent more and more of the military against them, the 12th Expeditionary Fleet struck from the Chode Sector. Primarch Roboute Guilliman dove into the Asgardia Sector to strike at the head of the Ur'Iso Ecumene before they could respond to his arrival. As planned by the Primarch, the Ur'Iso Ecumene struggled to adapt to the loss of their core territory.
Within three years, the 12th Expeditionary Fleet had secured not just the Asgardia Sector, but also the Chode, Damocles, Lostrix and Nurth Sectors, shattering the Ur'Iso Ecumene in the process. The 620th Expeditionary Fleet had secured the Mundi Sector and, due to the heavy losses sustained, was used as a garrison force before the survivors were folded into the 12th Expeditionary Fleet. Meanwhile Primarch Roboute Guilliman led the 12th Expeditionary Fleet into the Jericho Sector to hunt down the last holdouts of Ur'Iso Ecumene as the surviving xenos had its last colonies there.
In the Jericho Sector, the Ultramarines linked up with the Night Lords with the two Legiones Astartes fighting a bloody campaign there, one where the XIII Legion had no problem with the VIII using their iconic tactics against the Ur'Iso. With the extermination of the Ur'Iso in the Jericho Sector, the Ur'Iso Ecumene was considered destroyed and the xenos species destroyed.
While a watch was maintained until the events of the Horus Heresy took priority, no sign of any surviving Ur'Iso Ecumene forces was detected. That remained the case for the following nine millennia as the only Ur'Iso presence detected were the discoveries of old wrecks and abandoned ruins. Despite rumours of Ur'Iso ghost ships remaining constant in the region, no investigation into any supposed sightings by the Inquisition and Imperial Navy have turned up anything. Any such reports have been deemed 'spacer tales' and considered baseless.
The only modern presence of the Ur'Iso is their legacy as there is a small cold trade around their artefacts in the region. Additionally, the Adeptus Mechanicus often sends teams to investigate their ruins for reasons that they refuse to disclose, citing the Treaty of Olympus Mons when questioned on the matter.
The Ur'Iso were mammalian and roughly shaped like a human with two legs with feet, two arms with hands and one head. They had grey thick skin that was often described as leathery that provided a minor degree of protection. The face and muscular structure of an Ur'Iso was often described as bulbous and they had no visible nose or ears.
They also had a higher level of average strength and toughness than a mundane human albeit still below the strength and toughness levels of a Space Marine or an Ork. Beyond that, the Ur'Iso were fairly akin to humans in terms of biology with live births, carrying the child within the womb and a dependency on food and drink to survive.
The lifespan of an Ur'Iso was measured in centuries rather than decades. Whether this was due to an inherently long lifespan or commonplace usage of rejuvenat technology is unknown. The Ur'Iso appeared to reach adolescence in a decade, but it took a few more decades for an Ur'Iso be considered an adult. It is unknown if this was due to cultural or biological in nature, but the Adeptus Mechanicus' investigation at the time of the great crusade could find minor differences between an Ur'Iso adolescent and an Ur'Iso adult.
In terms of ground forces, the Ur'Iso Ecumene made heavy use of Abominable Intelligences, reserving actual Ur'Iso warriors for what were effectively officer roles. The bulk of any Ur'Iso army consisted of machine-soldiers and in skirmishes or guard posts, it was commonplace for the entirety of the Ur'Iso force to consist of AIs.
The first machine-soldier of Ur'Iso was the Sentry. Using anti-gravity to fly, the Sentry was deemed the most basic and often used. The average Ur'Iso Sentry was little more than twin anti-gravity generators, a hardlight gun and some armour plating. Even the intelligence of it was basic enough that there was even an Abominable Intelligence installed in a Sentry. While most Sentries were basic, the Ultramarines did encounter some more advanced ones, equipped with incineration weapons and/or energy shields.
The second Ur'Iso machine-soldier was the Hound. Named by the Imperium for being similar in design to a canid, the Hound had four legs and a hardlight gun in place of its head. Able to climb up onto walls and ceilings in addition to being extremely fast, the Hound was used as a scout and infiltrator by the Ur'Iso Ecumene. They would use them for recon missions and to spring ambushes on their enemies.
The third and final Ur'Iso machine-soldier was the Soldier. Fashioned after an Ur'Iso, a Soldier stood on two legs and wielded a gun with two hands. The Soldier acted as the common soldier of the Ur'Iso Ecumenee, which was how it acquired its designation. While most Soldiers were equipped with a hardlight weapon, a few used incineration weaponry and advanced models were equipped with energy shielding.
The last main unit of the Ur'Iso Ecumene were the Knights, who were flesh and blood Ur'Iso rather than AI machine-soldiers. Wearing thick and heavy armour comparable to Tactical Dreadnought Armour, the Ur'Iso Knights made strong usage of jump packs for mobility. Their left arm traditionally had a melee weapon while their right arm had a hardlight gun or an incineration gun. For additional defence beyond the heavy armour, Ur'Iso Knights were equipped with energy shields that provided protection on par with an Iron Halo or Rosarius.
In terms of ranking, every Knight was an officer to the machine-soldiers that make up the bulk of their armies, the Ur'Iso Knights had their own ranks amongst themselves. A Lancer was their equivalent to a sergeant while a Champion was their version of a captain. A Warden would command multiple Champions or an escort warship while a Castellan would be a commander of Wardens on the ground or the captain of a capital ship.
A Marshall acted as their equivalent of a general or an admiral while the highest known rank amongst the Ur'Iso Ecumene was an Archon. The exact nature of an Ur'Iso Archon remained unknown though it was largely believed to be the overall commander of an Ur'Iso version of a sector. It was unknown if each Archon was equal in rank or if there was some sort of internal hierarchy amongst them. It was also theorised there was a rank even above Archon, but there was, the Imperium never encountered it or found evidence of its existence.
The warships of the Ur'Iso could be divided up into four types. The
Greatsword-class Dreadnought, the
Longsword-class Galleon, the
Shortsword-class Carrack and the
Dagger-class Galley.
The
Dagger-class Galley was the only identified escort-sized warship of the Ur'Iso Ecumene. While it had its own warp drive, the
Dagger-class was often attached to a capital ship with the
Shortsword-class Carrack and the
Longsword-class Galleon being able to carry a pair of Galleys while the
Greatsword-class Dreadnought could transport up to four. As much as it pains me to admit it, in terms of combat capability, the
Dagger-class Galley was superior to its Imperial counterparts.
In terms of shields and turrets, the
Dagger-class Galley was fairly standard and in terms of speed and armour, it was on the higher end for its size though still within usual expectations. The firepower of the
Dagger-class Galley was where the xenos warship truly stood out as it had lance battery had both great range and firepower to it, beyond what any Imperial escort is capable of mustering. Furthermore, the
Dagger-class Galley has a hangar bay capable of supporting a few squadrons of Ur'Iso Gunships.
The
Shortsword-class Carrack and the
Longsword-class Galleon were considered the Ur'Iso equivalents of a light cruiser and cruiser respectively though that appears to be a judgement based on size, speed and durability than anything else. A
Shortsword-class Carrack had thrice as much firepower as a
Dagger-class Galley and twice as much hangar space, shielding and turrets, making it more comparable to a cruiser than a light cruiser.
Meanwhile, a
Longsword-class Galleon had triple the firepower and hangar space of the
Shortsword-class Carrack along with stronger shields and more turrets. Its immense firepower was beyond even a battlecruiser and was more akin to a battleship. During the Great Crusade, the Galleon was indeed reported to hold their own against Imperial battleships.
The last Ur'Iso warship is their greatest, the
Greatsword-class Dreadnought. With double the firepower and hangar space of the
Longsword-class Galleon, the
Greatsword-class Dreadnought was only outclassed by the greatest of the Imperium's battleships. That said, even the
Greatsword-class Dreadnought paled before the
Gloriana-class Dreadnought as the
Macragge's Honour was confirmed to have destroyed multiple Ur'Iso dreadnoughts in a single engagement on more than one occasion.
In terms of attack craft, the Ur'Iso Ecumene only deployed their all-purpose gunships. These versatile gunships performed the roles of both fighter and bomb in the void and were capable of providing aerial fire support in atmosphere.
While there are more extensive reports on the xenos technology of the Ur'Iso Ecumene by the Adeptus Mechanicus, I shall cover their most distinctive technologies here. The first of which is their hard-light technology where the Ur'Iso were somehow able to turn light into a solid state. This was the basis for much of their technology from their hard-light guns to their hard-light blades to their energy shielding. How this technology works remains unknown, but their handheld hard-light guns could hit as hard as a boltgun while their hard-light blades were comparable to a power sword.
The Ur'Iso also made extensive usage of hard-light technology in their architecture. Ur'Iso structures would often use hard-light doors while the xenos would heavily use hard-light roads and bridges. It has also been speculated that the Ur'Iso used hard-light for furniture like tables and seating.
Another notable technology of the Ur'Iso Ecumene was their other main weapon type, which would be their incineration weapons, which the Adeptus Mechanicus believes to be deprived from mankind's volkite weapons. These incineration weapons were rare, but destructive when used properly with enough firepower to overcome the power armour of Legiones Astartes. Because of this, the Ur'Iso used them as their equivalent to heavy weapons for when greater firepower than hard-light weaponry was required.
The Ur'Iso Ecumene were also noted for their extensive usage of Abominable Intelligences. In addition to using it for the majority of their military forces, the Ur'Iso used AI in every major building. Every location of significance had at least one AI installed and more extensive compounds were home to multiple Abominable Intelligences.
The last notable aspect of the Ur'Iso Ecumene was their heavy usage of megaprojects. The Ur'Iso constructed many great works during their time, viewing their megastructures as proof of their greatness and superiority. According to official Imperial reports, all of these xenos megastructures were destroyed by the Ultramarines during the Great Crusade though baseless rumours of surviving Ur'Iso megastructures continue to exist as 'spacer tales'.
The most common Ur'Iso megastructure was their orbital habitats, where the vast majority of their populace lived. A mixture of artificial ring worlds around stars and vast orbital habitats above resource-rich worlds, the Ur'Iso built these residential megastructures along trade routes. Something that proved to be a double-edged sword as while it enhanced the Ur'Iso Ecumene in times of peace, it also allowed for Roboute Guilliman to swiftly identify and assault the majority of their populace.
Other major Ur'Iso megastructures included the Matter Decompressor and Strategic Coordination Center. The former was a xenotech structure around a black hole that used the gravitational pull of the black hole to turn hard-light into raw materials for the vast industry of the Ur'Iso Ecumene. The latter was the centre of the centralised Ur'Iso military, where the Ur'Iso coordinated all of its fleets and armies from. Its destruction at the hands of Roboute Guilliman during his initial entrance to the war was a blow that the xenos never recovered from.
Another notable Ur'Iso megastructure was the Scientific Research Nexus, where the Ur'Iso Ecumene did all of their most advanced and dangerous research. It was destroyed in its entirety by Roboute Guilliman during the Great Crusade. While it was reported that Adeptus Mechanicus pushed for its capture for its xenotech to be studied, the Primarch of the XIII Legion was able to push through its destruction on the argument of how intertwined Ur'Iso technology was with their usage of Abominable Intelligences.
The last of the preeminent Ur'Iso megastructures was the rumoured Star Forge. The Star Forge was said to be powered by a star and able to produce countless warships and wargear for the Ur'Iso Ecumene. However, all evidence points to this not being true as if such a thing did exist, the Ur'Iso could have used to it to drown the 12th Expeditionary Fleet in a flood of xenos vessels. As things are, rumours of its secret survival or even the fact it existed in the first place can be considered nothing more than regional 'spacers' tales'.
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A small info primer on what the Ur'Iso Ecumene was since the Storm Avengers and the Iron Sentinels would certainly have some information on them. Hopefully it makes them a bit more fleshed out and give some more insight into the past of the Asgardia Sector.
Please point out any spelling or grammar mistakes that you spot. Please quote them in the thread and explain what you think is wrong so I know what you are referring to.
