User blog comment:DirgeOfCerberus111/Adeptus Custodes Vs. Grey Knights/@comment-33731050-20150327035801/@comment-33731050-20150327053243

Out side Horus Heresy do we see the Emperor Doing battle? Nope, and that's why the Custodus don't. There is nothing written about them doing anything but guarding the emperor after the Heresy becasue they never did, they guard the Emperor on his throne. That's it.

Writting fannon about Custodes outside the Emperor's palace during 40k would be NCF, that's why you don't see any fannon about it. Though Great Crusade/ Horus Heresy Era fannon about them would be great. There is really not enough written about that time on here.