Stannis did claim to wield it, but that believe was mistaken and was pretty evident in the books. The books did seem to indicated that it was a relic and possibly some other sword, though there was nothing definitive.Maybe I'm confusing the books and the show but shouldn't Lightbringer already be a relic at this point? Didn't Stannis claim to wield it?
Haven't read the books for a while though so I could be totally off base.