system
Given the following post, respond as if you're commenting on Reddit:
human
[WH40] An Emperor level person is born, now what?

So its clearly possible to create an emperor like individual, even in primitive conditions. So lets say we have some backwater planet, insignificant to the imperium. They pay the tithe and the guardsmen and whatever else is asked, staying well below the radar.

A whole bunch of the local phyckers put their heads together, literally and a year later this person is born.

So:

* When does he/she come to the imperiums notice?

* How does the imperium react?

* What position / job / fate awaits this person?

* What, if anything changes with the status of the emperor?
gpt
The Imperium notices.  The black ships cross the whole breadth of the Empire searching out newborn Psykers, bringing the weak to feed the Astronomicon, and training the strong in how best to serve the Empire.  Neither of these fates are acceptable to the new Emperor, who breaks free from whatever bonds the Imperium places upon him.

Next come the Inquisitors, hand-picked to deal with what is the most dangerous young Psyker the Imperium has come across in millennium.  They attempt to purge the young Emperor, but are instead made to kneel before him.  

The order of Exterminatus is given, and a fleet of ships comes to purge the planet he lives on.  With a thought, he steps from the surface of his world to the bridge of the flagship of the fleet.  It is his to control now, the beginning of a glorious new Empire.

From this seed grows a new Empire.  The stars are washed with blood in quantities unseen since the Horus Heresy.  The whole of the Imperium is first split asunder, and then regrown under his command.  After the final battle, the new Emperor arrives on Holy Terra, sweeping aside the custodes like a gnats before a hurricane.  He stands before the old Emperor, and smiles to him like an old friend.  He only speaks the words, "Thank you for all you've done.  You can rest now, the Imperium is safe."

The old Emperor finally crumbles beneath the weight of forty thousand years of life, and the new one takes his place as the new Emperor of mankind.

Later, he falls to chaos, and everything goes to shit.