Towards the ending of season 2, theres an episode(I forgot which one exactly) ember narrates all hes done to fuck with fillory e.g the wellspring brownouts. One of the things he mentioned was pissing off the river watcher, which made him angry when he met penny and ultimately led to him cursing penny's hands. This leads to Penny trying to find anyone who can help him. After numerous attempts he settled with the Library. At some point Kady is looking for a book to kill a god, books like that can only be in the poison room and penny is the only Liberian they know that could even attempt to do this. Penny ends up dying from the poison. Ember killed penny :)) . Makes me wonder if Penny's book had all this in it. On one hand they make it seem like the books are set in stone, but on the other hand Alice literally bleeds a stone to safe Q.