Board Thread:Lore Discussion/@comment-18016240-20131125000510/@comment-121511-20150421195535

As I said: main sources are out-of-game. The Arcturian Heresy is simply what links out-of-game sources to in-game sources, and the Ghost of Old Hroldan lends credence to it: it does not in and of itself detail the nature of the enantiomorph, but it makes mention of it, and tells the truer account of "Tiber Septim".