system
Given the following post, respond as if you're commenting on Reddit:
human
[Warhammer 40k]What are the long-term implications of the Emperor's death?

It has been rumored that the Golden Throne is failing and more and more psychers are required to keep him alive.  I understand that traveling the Warp will be impossible without the Astronomicon, but it seems to me that this would be the Blackest Night and the End of Days.  But assuming we survive the horrors of the Warp, what are the long-term implications?  The Empire would be sundered with no way to travel between worlds... but I wonder if the Emperor might be reborn...
gpt
There are currently 3 things that could possibly happen if the Emperor dies.

1) The Astronomicon falls apart, warp travel becomes extremely difficult, and because the Imperium is far too large, it will fall apart almost immediately. Regional warlords will assume power, Xenos factions like the Tau, the Orks, and the Necrons will be quick in exploiting Humanity's weakness, and many world will fall. The Hive worlds like Cadia, and Armageddon would hold out initially, but with the combined threat of Xenos invasions and starvation, they will eventually fall. Essentially, the Age of Strife happens all over again.

2) Star Child theory is correct, and the Emperor will be reincarnated. No one will believe that he's the Emperor at first, and many will try to oppose him, but after while he will unite the factions and remnants of humanity (just like after the Age of Strife), and lead the Imperium on another Great Crusade.

3) The Emperor gets reincarnated in the immaterium. He becomes shining golden god in the warp and completely destroys the Chaos Gods once and for all. Making warp travel safe and free of daemons while at the same time guiding humanity through the stars as a even more literal god.