If the emperor did not stop psykers at nikea but instead helped Magnus and the thousand sons master their abilities when Horus was injured in the davinite lodge he would heed Magnus's warning and not fall.
If the warmaster stayed loyal who would of the chaos powers turn to?
Lorgar would still be going against the emperors words so would still be punished and fall to worship undivided.
Angron would still fall to khorne. Would fulgrim fall if Horus was there to help him? Is mortarion always doomed to fall to nurgle?
I can still see the night lords becoming renegades not chaos but breaking away from the emperor.
I can also see Russ attacking the thousand suns still and falling to his pride. Not to mention the wolves are always seeking great fights and boasting stories of hunts washed down with a keg or two.
If Horus does not fall would there be a heresy or would it be a case of renegade legions only and a very different imperium with a living emperor.
Also what of the dark angels they had renegades in their midst and without the heresy would it remain hidden?
It's such an interesting thought if one thing was different how would it effect the timeline?
Please post your views.