Board Thread:False Info and Speculative Discussion/@comment-24.130.28.230-20150721180826/@comment-4091815-20160130192400

Your getting into the weeds here. Let's see if we can carve a path out for you. Deaton, as a longtime druid, is an expert on Mountain Ash and other substances and the various effects it might have on various individuals. If he says only non-supernaturals can cross a mountain ash barrier, as an expert, we believe him.

The hunter's diary is written by different people at different times in history. The information is at times contradictory due to the fact that various individuals at various times would have various levels of expertise. If the show quotes the book, then we can believe the entry being quoted because they wouldn't bother otherwise but the mere fact that something appears in the book doesn't cement its status in canon.