The Archive (so termed by Inquisitor Amberley Vail of the Ordo Xenos) is not to be confused with Cain's official autobiography, "To Serve the Emperor: A Commissar's Life". The archive was compiled while he was a tutor at the Schola Progenium, beginning around the year 993.M41. As stated by Inquisitor Vail, who spent some years editing and annotating the archive, there seems to be no order or chronology to the written accounts that were stuffed onto a single data slate.
Sadly, due to the sensitive nature of many of the accounts within, Vail was forced to place the archive under Inquisitional jurisdiction almost as soon as it came to her attention, sometime during 005.M42. The primary reason for sequestering the archive was to hide the fact that Cain himself admits to be self-serving and quite the scoundrel, contrary to his image as a Hero of the Imperium. The other reason is due to various interactions with xenos creatures and agents of Chaos.
Through the dissemination of the Archive to her colleagues in the Inquisition, Vail hoped to give her fellow Inquisitors insight into the minds of the alien races Cain interacted with, further understanding of the dark designs of Chaos beings, and the inner workings of Cain's own mind.