Concept: the Emperor's grand plan was to sacrifice humanity so that he might become a fifth god of Chaos. The Emperor sought to lure Horus down the path of corruption but he saw through his schemes. Rallying the other Primarchs who had not been corrupted by their father, Horus lead the civil war against the Imperium. At the siege of Terra Horus lowered his ship's shields in a desperate bid to lure the Emperor into attacking him and distracting him from the Emperor's plan. Horus duels the Emperor but is killed, not before mortally wounding the Emperor. With the Emperor dying the "loyalists" abandon Terra, leaving Horus's forces triumphant. The Emperor is imprisoned in the Golden Throne where thousands of psychers are sacrificed to keep him chained. The Imperium is largely ignorant to what really happened as the narrative was spun that Horus tried to rescue the Emperor from the "traitors" he was surrounded by. This was necessary as the Emperor is pivotal for Warp travel in the Imperium.
What do the legions look like? How do the different personalities of the Primarchs effect the galaxy with their places switched? What "loyalist" legions fall to worshipping the individual gods of Chaos?
Edited by Skaorn, 07 September 2021 - 12:54 PM.