Editing Primarch (section)

=== The [REDACTED] Event ===
 
*'''The First Heretic''' shows that by the Razing of Monarchia (43 years before the Isstvan V Drop Site Massacre of 006.M31), the II and XI Legions had already been stricken from the records. It also states that the remaining Primarchs had to swear an oath never to speak of their missing brothers and that the missing Primarchs' corresponding legions were personally purged by the Emperor, so it had to have been something extraordinarily bad. However, Lorgar still remembers something about them, saying "I still remember how they-", before Magnus cut him off. Lastly, it is revealed that the Emperor had considered purging Lorgar and the Word Bearers (making them the third legion to be purged) for starting a religion around him, but Russ had talked him out of it. #BlameLemanRuss
*In '''The Lightning Tower''' Rogal Dorn says that the lost Primarchs' disappearances were "separate tragedies", so it seems like they disappeared in two different incidents.
*In '''Descent of Angels''', which takes place as of the time Lion El'Jonson had been rediscovered, Chief Librarian Israfael tells the then initiate, Zahariel El'Zurias, that the Lion has 19 brothers; indicating that as of that time they had not committed whatever atrocity lead to their demise. This also means that the existence of the Primarchs was not a secret among the Imperium.
*In '''Dark Imperium''', Roboute Guilliman declares "I was one of twenty. Two failed. Half the rest turned on my Father." This suggests that the downfall of the two lost primarchs was not a result of them betraying the Emperor. Instead their demise was a result of them "failing" their purpose as primarchs and being terminated as a result. Interestingly this line also seems to imply that it is no longer forbidden to speak of the two missing primarchs in the 42nd milenium, as Guilliman casually references them to make a point about primarchs being fallible. (The 2021 revision of the book adds a bit more to this; it looks like the Imperium has covered up the fact that there were even two deleted Legions and Primarchs in the first place.) 
*'''The Chamber at the End of Memory''' has Rogal Dorn note that he was one of the few Primarchs who ever met with the II and XI Primarchs. It also reveals that not only was the entire Imperium forbidden to speak of the missing Primarchs' existence, but every non-Primarch save for Malcador who had ever interacted with them was mind-wiped so they would remember nothing about them - including their own gene-sons, presumably other than the fact that they were purged from all record and be left unable to speak even about that. Even the other Primarchs had their memories altered so they couldn't recall much more about their lost brothers beyond the fact that they existed - Dorn is dumbstruck by this discovery, and even more so when Malcador tells him that it was his own idea (and Roboute Guilliman's) to have his fellow Primarchs' memories altered. Malcador also states that '''whatever it was that the II and XI Primarchs did, it was against the very ideals of the Great Crusade and would have ruined everything the the Great Crusade had accomplished to that point.''' Their old living quarters in the Imperial Palace are protected by extremely powerful psychic wards, and when Malcador briefly restores Rogal Dorn's memories of them he realizes the '''''hateful truth'''. That '''the entire Horus Heresy up to the Siege of Terra was not so awful or threatening to the Imperium as what had happened to the Missing Primarchs'''; in fact, '''if they were still alive, the Imperium would have long since fallen'''.
*'''Deliverance Lost''' suggests that whatever happened to the missing Primarchs occurred sometime before the Emperor found Corvus Corax, as Corax asked the Emperor why there were only sixteen other Primarchs waiting for him if he was the nineteenth (it's unsure whether this was referring to him being the Primarch of the nineteenth Legion, or him being the nineteenth found); the Emperor avoided the question, claiming that "it would be a discussion for another day". This is no longer the case, somehow, as he is [[Retcon|now the third-to-last primarch found]], right before the second missing primarch.
*In '''Prospero Burns''', Leman Russ mentions that the Space Wolves had fought other Space Marines before the attack on Prospero, which may have something to do with the purge. A senior Space Wolf describes Russ' "wyrd" as being "the Emperor's executioner". Several books since have backed this up, though [https://www.reddit.com/r/40kLore/comments/8q7qyg/the_space_wolves_what_were_they_really_for_little/e0hih9h/ ADB denies this].
*In '''Scars''' there's a reference to rumours and "whispers of past atrocities" that only a Primarch could kill another Primarch. Russ also turns up and talks a bit about fighting Magnus, and the resulting "shame". So if he's responsible for offing one or two of his brothers, they must've done something pretty fucking heinous.
*In '''The Dark King''', when asked if he will report the Night Lords for censure, Dorn remarks that he feared to add another empty statue to the Emperor's palace, implying that the missing legions were exterminated for committing severe atrocities.
*In '''The Last Council''' Malcador states that one of the missing Primarchs was '''fallen and disgraced'''. Alpharius mentions that one of the primarchs had died. While the lost Primarchs and their Legions were wiped before he was rediscovered, its Alpharius....you can't keep info like that from him.
*Their legions were purged in the times of the [[Rangdan Xenocides|Rangdan Wars]] they participated in.
*In '''The Wolftime''', which is set during the [[Indomitus Crusade]], two Adeptus Custodes are discussing the Space Wolves' resistance to their new [[Primaris Marine]] reinforcements. During the discussion, one of them, Hastius Vychellan, notes that, if [[Roboute Guilliman]] turned on the Emperor, the Space Wolves would be among his first opponents, as the Custodes' history with the Eleventh Legion demonstrates. The other, Maldovar Colquan, notes that this shared history is an example of how loyalty to the Emperor can be corrupted by lies and manipulation. It's quite vague, but the implication is obvious: someone manipulated the XI Legion into turning traitor without them realising it, and the Space Wolves (and likely the Custodes as well) went after them for it. The book doesn't say who manipulated them, but since Malcador mentions in ''The Chamber at the End of Memory'' that the lost Legions' Marines were spared and re-used after their deletion, but the Primarchs weren't, it's possible it was the XI Primarch.