A Legion at War

A Legion at War was an Imperial xenodical purgation campaign carried out by the Omni Legion Space Marine Chapter and their Adeptus Mechanicus allies from the nearby forge world of Roitheta to rid themselves of an encroaching invasion forces of Orks.

History
The centuries that followed the first campaign of the Omni Legion would would carry on like every moment had before, no one truly noticing them vanish from all battlefields. Only a handful of archived reports that speak of their 1st Formation and the battles they participated in, never leading one themselves. Despite how young they were the Omni Legion was a name that several Chapters would hear about from the Salamanders and Terra's Cockroaches. The High Lords of Terra would constantly have the Chapter and the Forge World that claimed to have created them on watch and have reports about their actions every moment that they could to ensure their loyalty.

The Forge World of Roitheta created the Chapter's second Battle Barge and additional support ships, creating a fleet which would operate separate from the 1st Formation. As the 1st Formation led an expedition that led them to their first encounter with the Dark Angels the rest of the Chapter was dispatched to the Tallon Prime system after reports suggested an Ork fleet was attempting to attack the world. The 2nd, 3rd and 4th Formations would be dispatched to counter the xenos days in advance.

Once the greenskins entered the system their fleet was besieged by the Astartes ships, the enemy fleet was smaller than expected and was quickly driven to a world distant from Tallon Prime, the Ork forced to this other world. It would be mere hours before the entire fleet had either been destroyed or crash. The Chapter would deploy it's entire force with support from the Mechanicus of Roitheta, mostly working as witnesses to evaluate how efficient they were. This was the first time in Imperial records that the Chapter was seen on a scale lager than 200 in nearly 400 years. Most of the Chapter's strength swept through the Orks, ravaging the Dead world they had fallen upon. No care was given by the Legionnaires, the world held no value to the Imperium so tactics and ranged weapons they used, was in many cases, overkill. Those who had lived through the Great Crusade or Horus Heresy would compare the Omni Legion to the Iron Warriors of old, based on the wrath they instilled upon the Orks.

Mere days would pass as the flaming wreckage the Orks used as their own shelter was torn apart from heavy artillery and their infantry was overwhelmed by the Space Marines. Like an avenging phoenix rising from Hell itself, the Omni Legion was unlike they had been on Patron, the fury they unleashed was only fueled by their hatred of the xenos and the very idea that they had intended to attack Tallon Prime. They threatened the civilians of the Imperium, such an act could only be answered in bolter and fire. With the Orks seemingly slain with few casualties the Omni Legion bombarded the planet to ensure the remains of their ships couldn't be salvaged in case a single Ork attempted a feet of immeasurable magnitude by slapping together a single shuttle to escape. This was their true rise and display of might to the galaxy at large, no one would dare threaten the Imperium if they didn't expect to battle fierce warriors such as them.