A Thousand Sons by Graham McNeill | Book Review | Horus Heresy 

I like to think that when the Emperor psychically speaks to Magnus right before giving the verdict of Nicea, he's saying something along the lines of "HOW DARE YOU MISREPRESENT THE ENDING OF THECAVE ALLEGORY, I WAS THERE WHEN MY MAN PLATO FORMULATED THAT STUFF" and decided to rule unnecessarily harsh and reject the librarian compromise just because he was really mad at Magnus for that.

My favorite part of this book is when Magnus realises he broke his daddy's project and proceeds to hide in his bedroom until the custodes & wolves arrive (I'm assuming this takes at least a week). Then he turns the planetary shield off so that the bombardment annihilates all the people. He also makes the brave choice of not letting the thousand sons now anything about what is happening, which leads them to massacre bunch of the custodes. The real tragedy about Magnus is how throughout his life, he thought he knew better than anyone else. Everything he was forbidden to do, he did. Even 'fixing' the flesh change was done by someone Magnus met during his warp traveling, probably Tzeentch himself. As far as Primarchs go, Magnus is no doubt the most angsty one... Morty and Perturabo share the second place.

Personally I think Prospero Burns has a more interesting approach to the same event, this one feels a bit like banal anime plot Also you forgot to mention the *OIL*

He did wrong but man he didnt need to get hit by the belt this hard