As the title states: 'Nothing they do matters', well, that's the problem I considered when I finished reading one of my favorite fantasy book series, the Belgariad. The problem, as I saw it, with a prophecy that has to come true, is that no matter what the characters choose to do in the story, does it really matter? The prophesy says the way it will be, and so it is. So when I started thinking about prophecies and how they are handled in fantasy, I got the idea for part of the story concept for the NexLord series.
If I was to put a prophecy in a book, how could I have a prophecy that would come true, and still give the characters choice that mattered? So I tested the theory of self fulfilling prophecy in a table top game. I wrote a prophecy, gave it to the players, then didn't force it to come true, and yet the players made every bit of it come true. My conclusion was that when you think you know the future you make the future fit into your belief.
And that took me down the path of belief, and how a person uses a similar process in their belief system. More than that, I considered how the power of a lot of people believing in the same thing influences others, and reinforces what the group believes. At that point I applied my 'What if' principal (See Chocolate Manhole Covers in an earlier post) and said, "What if the power of belief could actually make that belief true? Meaning, the more people that believed in something, the truer it became.
Then, assuming that was true, how would that work with a prophecy? Once this power became known to people, how would they use it to manipulate the world? And after a lot of consideration, along came Dark Prophecies, the first book in the NexLord series, and (among other things), my exploration of prophecy and belief as a real system of 'magic'.