You have a few options, depends what method you’re most comfortable with. You could use an edible image on some strengthened fondant cut to the shape. You could cut the shape and then paint/airbrush it once the fondant is dried or you could build it like a mosaic. Whatever method you need a template of the sword to handcut the shape from strengthened fondant. Don’t know it that helps at all… I have a tendency to ramble ;)
Mel, Yorkshire, http://www.facebook.com/doncastercustomcakery