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[Warhammer 40k] The potential of having a God of Order in the Warp.

Say the Emperor finally dies and manages to fully manifest in the Immaterium, powered by the hope and dedication of the people of The Imperium. 

Could he fight and subjugate (or even kill) the four main Chaos Gods? Is such a thing even possible given how each represent an inherent part of sentient life?

Can he go beyond that and actually be able to control or "calm" the Sea of Souls to a the point it is safe for travel like during when the Old Ones were around?
gpt
The Emperor doesn't represent hope and dedication. He never did, and never will. The Emperor represents Guardianship of Humanity. He's not a God of Order, but a Human-centric war God and Guardian, something akin to a hybrid if Khaine and Vaul for the Eldar. 

It IS possible to kill a God, however. If a sufficiently powerful warp presence, with enough overlap, absorbs them, they seem to maintain their core identity while taking on the expanded influence of those they 'devour'. This is what happened with the Eldar Gods and Slaanesh. 

In order for the Emperor to succeed, he would have to have far more power than the Chaos Gods, but also represent a sizable portion of their nature. Khorne and T-bird, maybe, but Nurgle and Slaanesh have little to no overlap with the Emperor.