Mirror Universe: The entire premise Dornian Heresy is this while it remains Grimdark, it switches the places of the loyalists and traitors, and in almost every major event the alternate choice was made.There is still at least one surviving loyalist primarch whose location is, to an extent, known, and there are fewer true traitors.

Lighter and Softer: As compared to the Horus Heresy.

No one took this lesson to heart until it was far too late. This, for a primarch, should be impossible, and should have indicated that strange happenings were about.

Ignored Epiphany: Horus was lain low and almost killed by a disease on Davin.Gone Horribly Right: Elaidanath was looking for a timeline in which the Death Guard did not turn traitor.The fact that the Emperor chose to do so, in Russ' eyes, is a traitorous act of the highest order, and he stormed out of the Council of Nikea in a rage. What drove him to side with Chaos and become a Khorne worshiper is Magnus convincing the Emperor to perform the soul-binding ritual on him. Fatal Flaw: Leman Russ' flaw is his Irrational Hatred towards psykers, especially Magnus the Red, despite him being his brother.The process rendered him completely blind, but gave him the ability of second sight in exchange. And after the Council of Nikea, Magnus privately approached the Emperor with a request to perform the soul-binding ritual on him and the Thousand Sons, both as a protective measure against Chaos and to assure the Imperium of his legion's loyalties. Here, Magnus' loss of one eye was attributed to a demon of Tzeentch taking out one of his eyes as an infant before his incubation pod crashed on Prospero, his missing eye being replaced with an 'ugly welt of scar tissue'. Disabled in the Adaptation: Canon Magnus is one-eyed, though how he got that way is Depending on the Writer.

Horus heresy tv tropes