This could be a reference to the rediscovery of the mysterious Alpharius, as he was the last primarch to be found during the Great Crusade, and his homeworld has never been revealed. 'And the Emperor forbade us to speak of it again. The complete and utter erasure of all records of the II and XI Legions is considered by Imperial historians as the most successful Edict of Obliteration ever carried out in Imperial history. While the Blood Ravens are of an unknown founding, their codes of battle align with those of the Codex Astartes.

In the novel A Thousand Sons by Graham McNeill, during the Triumph of Ullanor, Magnus mentions the missing primarchs to his brother Mortarion: 'Brother,' said Magnus, ignoring Mortarion's words. In the novel, The Unremembered Empire by Dan Abnett, when Lion El'Jonson arrives upon the Ultramarines' capital world of Ultramar, his brother Roboute Guilliman pulls him aside to speak to him about his plans for an Imperium Secundus. 2) Abbadon is an icon of hate, no question. The Primarch Leman Russ had been charged by the Emperor to take his Space Wolves Legion to Ghenna to bring the World Eaters to heel: (Kasper Hawser) 'There's a first time for everything. But he has a REAL beef with the Blood Ravens.

Blood ravens thousand sons