It was a legendary time. The Great Crusade carried the light of the Imperial Truths into the darkest corners of the Galaxy, returning the scattered worlds of humanity to the fold of the Imperium and erasing alien races from the face of history. By the will of the blessed Emperor, who decided to retire from military affairs, the reins of this unprecedented campaign were handed over to Horus, Primarch of the Luna Wolves Legion.

So the chronicles say, but in none of them can one find an answer to the question of when, under the sky of which world the seeds of the Great Heresy sprouted. Maybe it happened on the day Horus killed the Emperor for the first time...