Most of the history of Draconis IV can be found in the Draconis Coalition and the history of Draconis III, but this article will expand more on the history of the forge world of Draconis IV itself.
Draconis IV is a relatively new forge world, founded during the Great Crusade shortly after the Imperium welcomed the Knight World of Draconis III back into its fold. Shortly after Shogun Yato Yoshinobu of House Yato negotiated treaties with the Imperium, he was able to entice the Mechanicum to found a forge world on what seemed like a barren planet in the Draconis system. The fourth world from the sun of Draconis, it was apparently uninhabited, but the tech-priests of the Cult Mechanicus discovered plenty of ores, minerals and other resources under the rock of the world. Within years, Draconis IV flourished as a forge world as millions of tech-priests and their indentured servitors and laborers flocked to it, to claim the world's riches for their own, and also to conduct their own independent research.
The first and most powerful of these tech-priests was Archmagos Kent Rolov, who was recently exiled from Mars because of heretical thinking. He had once maintained close ties with Koriel Zeth, the Mistress of the Magma City. Having proposed innovation and creativity as the way forward for the Cult Mechanicus, emphasizing that change and progress is the way forward, and the only way to uphold the first credo Knowledge is Power, he was seen by many as a heretic and thus he left Mars before the Fabricator-General Kelbor-Hal could take any action against him. Arguing that knowledge can only be power if the Tech-Priests were willing to expand their knowledge through innovation and creativity, exploration and experiments, Rolov believed that both power and knowledge will stagnate if the Mechanicum refused to advance and attempt new things. However, with his status, he was able to become Fabricator-General of Draconis IV and continue his creed of innovation and progress in a sector distant from Holy Mars. Draconis IV became a hotbed for eccentric Tech-Priests, whose views were often considered borderline heretical by their compatriots. Pariahs, ostracized Tech-Priests, outcasts and even the frequently shunned Magi Dominus in charge of terrifying Legio Cybernetica cohorts sought refuge in this new Forge World, whose first settlers claimed authority and welcomed variety. Many of the Tech-priests were exiles from Ryza, having been hunted for pursuing new paths in plasma technology, and they arrived in Draconis IV to continue their supposedly blasphemous research. They brought with them scattered maniples of Skitarii, personalized cyborg armies more loyal to their individual Tech-priest masters than any overarching Martian priesthood.
Shogun Yato Yoshinobu was a shrewd politician and cunning warrior who recognized the need of the three Knight houses to rely on the Mechanicum. Despite having hundreds of aging Knight suits, he realized that their eventual wear and tear had rendered them all but ineffective in combating Xenos and the enemies of Mankind, particularly when he was treated to a display of power by the Imperial fleet who found them. As such, he was quick to forge an alliance with Archmagos Rolov, yet at the same time maintain the sovereignity of his House, as well as that of his allied Knight houses. House Yato, House Uesugi and House Takeda greatly depend on Draconis IV to construct, maintain and repair their Knights, the grateful Tech-Priests enthusiastically upgrading and repairing the aged suits both for their new allies' benefit, and also in order to receive protection from hostile agents under Martian authority.
Archmagos Rolov also expanded on his fledging Forge World's repertoire by trying to imitate the success of the revered Ryza. With many of the disaffected tech-priests coming from Ryza, Draconis IV's plasma technology developed rapidly and they were soon manufacturing Leman Russ Executioner tanks and countless plasma guns for the newly raised Solar Auxilia regiments in Draconis III that served alongside the Knights of House Yato. They also constructed entire columns of the super-heavy Stormblade tanks. It is said that Draconis IV produces exclusively Leman Russ Executioner tanks and Stormblade tanks, eschewing the other Leman Russ variants because it is simply easier to build tanks that rely on plasma reactors and energy weapons such as plasma cannons and lascannons than to continually manufacture and supply them with expendable munitions such as bolt shells, battle cannon rounds, Vanquisher anti-tank shells and demolisher rounds. Most of the weapons produced on Draconis IV are primarily energy-based, with las-weaponry, volkite weaponry and plasma weaponry constituting the majority of them. Rarely do the Draconian regiments use ballistic-based weapons such as autocannons or missile launchers. Instead, they are armed with lascannons, plasma cannons and even volkite culverins. For small-arms, they have the Draconis IV-pattern lasgun, along with Draconis IV pattern plasma guns, which aren't that different from those produced in Ryza. The mainstay of Draconis IV continues to be Leman Russ Executioner tanks, and even in the 41st Millenium, the Draconian Armored Defender regiments field entire columns of Leman Russ Executioner tanks. Draconis IV is also known for building the rarer pattern of Carnodon tanks, these medium tanks sporting rare volkite weaponry often not found in any other Imperial Guard regiments.
This specialization in plasma, volkite and laser weaponry extends to the Knights and Titans of Forge World Draconis IV. The Knights of House Yato are usually known for fielding more Knights Errant and Knights Preceptor than other houses, with thermal cannons and las-impulsors being manufactured in greater numbers than usual. The Dominus Knights Castellan are favored, given their plasma decimators from the forge-temples of Draconis IV. Armiger Knights Moirax are armed with the very rare volkite veuglaires, as are the volkite-based armaments of Questoris Knights Styrix given to House Kanda, a branch of House Yato dedicated to serving alongside the Titans of Legio Draconis. The Dark Dragons share the same inclination toward plasma as the forge world that they call home, the Warlord Titans often sporting Sunfury plasma annihilators and the venerable Warmaster Titan bearing twin plasma destructors. Such is the reputation of plasma technology produced by Draconis IV that it is known as the Second Ryza.
The people of Draconis III revere the sun, worshipping the Emperor as a descendant of the Sun Goddess, and this influenced the tech-priests of Draconis IV somewhat. The Cult Mechanicus in Draconis IV also holds special veneration for the sun, and they view plasma as the aspect of the Omnissiah as a descendant of the Sun Goddess, a partner to the Machine God, the two linked together by the Motive Force. That explains why they focus so much on plasma, with its ability to produce the power of a sun.
The Draconis Sector did not suffer much during the Horus Heresy, though House Yato often sent forth Knights to fight for the Emperor. The Titans of Legio Draconis, having sworn fealty to the Emperor, also sent forth their small maniples of massive Titans - often composing of Warmaster Titans and Warlord Titans alongside their vassal House Kanda to fight alongside House Yato. At their feet marched the Skitarii Legions of Draconis IV, ranging from Secutarii Hoplite Phalanxes to cyborg cavalry riding on fire-breathing mounts to armored formations of skimmering hovercrafts filled to the brim with cyborg soldiers. In line with their tech-priest masters, the Skitarii of Draconis IV field a high number of plasma calivers, though they also favor arc weaponry. The Tech-priests of Draconis IV sent Mechanicum cohorts and Skitarii maniples to fight for Ryza, helping the devastated world recover after Horus Lupercal's forces raided it, and also to help reclaim Mars in the aftermath of the Siege of Terra.
Yet, they weren't always welcome. In addition to their cyborg Skitarii, the Mechanicum military might of Draconis IV was constituted mainly of Cybernetic automata. Being in line with their tendency toward plasma, they produced an unusually high number of Thanatar siege-automata. Even their Castellax battle-automata sported Darkfire cannons and plasma cannons (similar to the Castellax-Achea battle-automata unique to the Thousand Sons) instead of Mauler bolt cannons.
For ten thousand years, Draconis IV has continued to manufacture plasma weaponry for the wider Imperium, as well as countless Guard regiments in the Draconis Sector. Over the millennia, Draconis IV has expanded its influence, becoming a lynchpin in the chain of forge worlds within the Draconis Sector, known as the Helios Forges, most of whom specialize in manufacturing plasma weapons. Unfortunately, a large swathe of them have been cut off during the opening of the Great Rift, and now that the Astronomican has returned, Draconis IV is launching a solar crusade to reclaim all those forge worlds that were supposed to be under its rule.
The Skitarii Legions have been mobilized. Armed with plasma and arc weaponry, as well as exotic technology, phosphor-based armaments and cyborg steeds, these augmented warriors will launch a crusade throughout the Draconis Sector and reclaim vital forge worlds, STCs and data for the Omnissiah!
Now coming up with a Forge World Dogma for my personalized Draconis IV is difficult. On one hand, I am tempted to just go with Data-hoard Forge World because Draconis IV is a forge world that collects data on plasma technology, Cybernetica production and STCs on Knight suits. They also include very radical Tech-priests who have been exiled from other forge worlds because of borderline tech-heresy, welcoming them to innovate and improve on plasma weaponry and also arc weaponry (though it's pointless because of how my Secutarii Hoplites don't benefit from the Forge World Dogma). My first choice is to pick the Magnabonded Alloys primary ability and then pair it with the Autosavant Spirits secondary ability to make my vehicles a lot tougher. After all, in addition to producing Knight suits for House Yato and building the massive Titans of Legio Draconis, Draconis IV is famous for manufacturing Cybernetica automata and vehicles such as Skorpius hovercrafts and Archaeopters. With so many Cybernetica models in my army (the Kastelan robots, anyway), this will benefit them. I wish we can field the Forge World models of Castellax battle-automata and Thanatar siege-automata, but we still do not have any 9th edition rules for them, and I doubt we will ever get rules for them. Oh, well. "Play Horus Heresy instead," some of you say, and I hear you. But then Horus Heresy doesn't have rules for my Skitarii, which sucks. We'll have to depend on the Road to Terra Podcast for that...
I am also tempted to look at Expansionist Forge World, which does fit my crusading Draconis IV - who has formed a chain of forge worlds known as the Helios Forges - but none of the abilities actually match the army I have in mind. Okay, sure, the Accelerated Actuators ability might help my Serberys Sulfurhounds and my Kastelan robots (who don't really need the additional AP for their Kastelan fists), but Forward Operations? My army is made primarily out of Cybernetica robots and vehicles such as the Skorpius hovercraft, and I have like, maybe 4 Skitarii Rangers squads - who make up a small percentage of my entire army - who will benefit from that, but that's it. I don't need the bonus to Rapid Fire weapons from Acquisitive Reach because the bulk of my army doesn't use Rapid Fire (again, my Skitarii Rangers...and we all know their Galvanic rifles will be Heavy 2 in the new codex). Last of all, Rugged Explorators...but the only dudes I have with Assault weapons are Skitarii Vanguard, which I rarely have (I do have 2 squads, filled to the brim with plasma). Not exactly what I was having in mind. Well, the changes to the Cognis weapons turn them all into Assault, so they might be useful to my Skorpius vehicles (cognis heavy stubbers) and Archaeopters (who don't need to advance, so...). Perhaps grabbing a few Ironstrider Ballistarii might be a good idea, but I'm not very keen on that. And if I do that, I might as well go with the Data-hoard Forge World to make my vehicles more resilient anyway.
Well, the new Adeptus Mechanicus codex will be arriving...soon. So we'll see! Perhaps we'll get new custom Forge World Dogmas. That will be something to look forward to.