This is the sword from Dagren the Orcslayer, extracted to a single sword model so it can be used as an attached effect. For best results, attach it to the right or left hand of the hero.
Edit: As a note, I made the sword 30 or 40 times smaller so you can attach it to a WoW model that's being used directly, rather than a WoW model that was ported and rescaled. Obviously feel free to scale it back up 30 or 40 times as needed.