Anaïve character might prove an unreliable narrator because the character

will lie for his or her own benefit
will not fully understand the events he or she witnesses
is not very smart
is often mistrusted by others

moon-letters were a method of writing invented by the dwarves. moon-letters were ordinary runes, but written in such a way that they could only be read when the light of the moon shone behind the writing. some moon-letters could be read by any moonlight, but it was possible to make the writing even more secret. more sophisticated moon-letters could only be read by the light of the same shape of moon, or at the same time of year, as when they were written. hope this !