The answer is simple.
Emperor siding with chaos.
Malcador and the emperor play many games of regicide and through them various plays are made with the pieces primarchs chaos corruption resistance to stay loyal resulting in various outcomes.
The chaos knights also known as renegade knights daemon knights and the questor traitoris in high gothic are imperial knight combat walkers their fallen noble pilots and knight houses corrupted to the service of chaos.
So i was watching an ach warhammer video about chaos lore and one statement he made has stuck with me for a bit.
I am not fond of human suffering and thus am against chaos.
Chaos exists only to feed itself and feeding itself requires humanity to suffer.
Humanoid war engines that tower over their foes each chaos knight carries an army s worth of firepower upon its weaponised limbs and hulking carapace.
However there are several plays that are made where malcador expects a specific outcome and is instead met with a surprisingly opposite outcome.
He raised the idea that maybe given the unwavering devotion that the imperium had now given the god emperor that there was a possibility that in that devotion the emperor had been able to manifest himself within the warp as a god what are peoples thoughts on this have i read it.
I would side with the emperor just as i would always side with the imperials in any conflict in 40k.
We also know what the deal was the warmaster made the same deal though he bargained to get it whereas the emperor took it by force.
Plus the deal isn t just known by chaos the perpetual alivia sureka who was asked by the emperor to seal the cave on molech after the emperor took the powers also corroborates the story.
How the emperor got his powers.