I fear that the question sounds vague and confusing, but I can't conjure up the words I need to say exactly what I mean without going into detail.
I thought it would be interesting to have two stories going on at the same time. The main story would be the events as they actually happened. It would be fairly straight forward stock fantasy style.
The second story would be someone several hundreds of years later in a modern time trying to tell someone else the same story. There are several things that were lost, added to or changed in in the telling. The story teller believes that the characters may have been based on real historic people, but it is likely the events were greatly exaggerated or never even happened at all. The story teller also believes that good and evil were very obvious and, simple and complete. In the "real" version, it's much more ambiguous. No one is really good or evil. The second story would be very short. Perhaps it is only a sentence or two long at the beginning of each chapter.
I think I've read a book or watched a movie set up like this. But I can't think of what it could have been. I'd like to know if anyone else might be able to think of an example of this situation so that I could find it. I'd like to read or watch it again to see how it was done.