The Narrator of the Forgeworld Heresy Books
Thus far, each Heresy book by Forgeworld has begun with a preface by an unknown individual. They provide no signature, but instead close their preface with a seal that contains the letters "AK". More tellingly, this individual is qualified to be "only human": "... not Primarch, not Legiones Astartes, not Custodian, not Mechanicum. Not even one of those courtly augments who bitterly cling to the threads of life to exist on in a living horror of alchem-treatments and stolen youth."
I did some searching through the Dramatis Personae of the Horus Heresy novels, and in Flight of the Eisenstein I was reminded of Amendera Kendel, an Oblivion Knight of the Storm Dagger Witchseeker Squad - one of the Sisters of Silence. Tellingly, she survives the events of this novel and is one of the individuals Malcador recruits for his nascent Inquisition.
What do you think? Could Kendel be the "in-universe" author of these volumes?