My apologies if this question has been asked or clarified before, but I've had a bit of a think about it and I'm confused. I would be grateful if anyone knows any additional information, or is able to clarify.
So, the Enchiridion is the holy text of the Ishgardian Orthodox Church. As far as I know, the church was founded some time after the founding of Ishgard itself, which was some time in the 550s of the Sixth Astral Era (Encyclopaedia Eorzea p. 47), though the elezen in Coerthas prior to that certainly worshipped Halone.
A merchant in Ul'dah claims to have a copy of the Enchiridion from the Fifth Astral Era. (Screenshot.) Okay, fair enough. We know that the Twelve were worshipped as early as the Third Astral Era (EE p. 17), and that cults or churches dedicated to individual members of the Twelve first arose in the beginning of the Fifth Astral Era (EE p. 30). It is entirely plausible that the ancestors of the Ishgardians, prior to migrating into Coerthas in the Sixth Astral Era, worshipped Halone and wrote the Enchiridion then.
However, the description of the Shiva Triple Triad card (screenshot) says that the Enchiridion describes Shiva as the Original Heretic, who lay down with dragons. Shiva lived in the mid-4th century of the Sixth Astral Era (EE p. 47). If the Enchiridion refers to Shiva by name, it must postdate Shiva's life. If so, what on Earth is the merchant in Ul'dah selling?
Several possibilities spring to mind as solutions to this problem.
Possibility one: the Enchiridion does postdate Shiva, and the Ul'dahn merchant is just lying. The customer is trying to sound intelligent but stupidly doesn't know when the Enchiridion was written or has misidentified an earlier Halonic holy text, and the merchant is accommodating this ignorance in the hope of making a sale.
Possibility two: the Enchiridion was in fact written in the Fifth Astral Era or earlier, but at some point in its early history the Ishgardian Orthodox Church falsified the text. They may have added new references to villains, or added entirely new chapters, or in some other way added Shiva, and then passed it off as what the text said all along. That would make a Fifth Astral Era copy of the Enchiridion incredibly rare and valuable, since it proves that the text has been modified.
Possibility three: the Enchiridion is not, in fact, a single text. Like the Bible or the Tanakh, it is a collection of multiple books, written at different times, which are usually bound together into a single tome for convenience. Thus the Enchiridion may contain Halonic texts dating back to the Fifth Astral Era or even earlier, and also contain later texts that were written after the founding of Ishgard. (This makes some sense in light of what the word means: Enchiridion literally means 'handbook', so maybe it just means a handbook-sized collection of Halonic texts.)
Is anyone aware of any sources I might have missed? What's going on with this text?