The backstory is excellent, and really ties the swords into the setting. However, I'd like to see a bit more about the blades themselves. Some ambiguity is nice for letting a GM weave it into the world, but too much ambiguity makes it harder to integrate them in, because more work has to be done to flesh them out. Also, considering this is a plot, some hooks would also be nice.
This definitely has potential, and I'd like to see it rise to that potential.