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[WH40K] What if the Emperor survived the Horus Heresy

We know that the Emperor's fight with Horus during the Seige of Terra mortally wounds the Emperor and forces him to be on the Golden Throne for the next 10 millennia, barely clinging on to life. But say, in an alternate timeline, the Emperor manages to win against Horus with only moderate injuries. How does the Warhammer 40,000 universe change with the continued existence of the Emperor?
gpt
The Emperor decides to make Chaos a priority. Psykers are hunted down and killed. Psyker Space Marines and Librarians are forcibly inducted into the Grey Knights or die during the 666 Rites of Detestation. The Legions probably remain as they are instead of being broken up into Chapters. Corax wouldn't be suicidally depressed, as the Raven Guard would be restored. 

The Cult of the God-Emperor is brutally repressed, with Saints being treated the same as any other psyker. Lacking a central figure to worship, more and more citizens turn to the Chaos gods. An expanded Grey Knights and more zealous Inquisition keeps Chaos at bay, but the Imperium is rent by many small wars over belief and religion. 

The Emperor finishes work on the Webway project, and starts his next big project to completely seal off the Warp by reverse-engineering the Cadian pylons and constructing them all over the galaxy.