This is a general history of the Magna System (subject to much future change). I am sorry to say I don't have star dates, but this is the order of events in system, leading up to the Invasion of Igneus Silicius, which might be story, but is actual a campaign I have planned with my friends. So that'll determine the outcome.
Records Expunged means contains spoilers, so I left it out.
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General History:
Establishment of Domum – Colonial excursions deem fourth planet in system habitable, and subsequently settle it. Within decades Domum has become a booming industrial center, and the Magnite Imperial Guard are founded. They are soon sent off to bolster nearby assaults on the Tau Empire.
Eldar Arrival – A smaller Craftworld, Craftworld Shelwe arrives in system, observing events.
Magnite Regiments Return – Forces sent to assist in the assaults on the Tau Empire return after years of fighting. The original commander, now Warmaster Lazarus, is crippled, and given a governorship. Within years, he has gone vegetative, and his adjutants assume command of the government. The planet falls into deep depression.
March Rebellion – Records Expunged.
New Governorship Granted – The Magnite Imperial Guard are localized as a defense force, and the Imperium takes a greater interest in the system as nearby planets are industrialized. The system becomes an economic center.
Chaos Return – Records Expunged.
Space Marines Arrive – A detachment of Blood Angels Astartes arrive in system, setting up recruiting stations on the harsh jungle world of Templum. This quickly becomes a prime military recruiting planet.
Hive Fleet Mastodon Arrives – Coming from a vector previously unused by Tyranid, a new Hive Fleet arrives in system, designated as "Mastodon." The system is hit hardest around the core planet Templum, and the hive world Igneus Silicus. The Blood Angels and System Defense Force react, and a long running battle ensues.
Tau Arrive – The Fi'Rios contingent, a deep penetrating Tau group, arrives in system near Templum. They are under the directives of 1) enacting diplomatic communication with natives, 2) preparing planets by force or diplomacy for colonization, and 3) holding planets for Tau colonization. They are met by aggressive defensive emplacements by localized forces, and are driven off. They switch their strategic stance to offensive.
Hive Fleet Mastodon Driven Off – The main bulk of the Tyranid invasion is driven off, but resurgent infestation is a daily occurrence on most planets.
Imperial Shadows Founded – Amidst a short peace time, the in system Blood Angels decide to focus their efforts on still prevalent Tyranid, and break off from the Blood Angels, becoming the Imperial Shadows.
Tomb World Glacialis Tundra Awakens – Following Eldar spotting in system, the Imperial Shadows move to the Mechanicum outposts on Glacialis Tundra, a remote world. They are faced with Tyranid resurgences from Mastodon, Eldar offensives, and Tau insurgencies, working on Eldar intelligence. This world is revealed to be a Necron Tomb World, but with a joint effort on all sides (excluding Mastodon) it is neutralized.
Tau Insurgency of Igneus Silicus – The Tau enact the second directive of their plan, invading the main economic center, Hive World Igneus Silicus. Imperial Shadows and Magnite Imperial Guard react.
