Subaru has talked of Balmung before and we hear about him being a great warrior. When we finally do see him Subaru refers to him as "High Class Balmung." Also, Sora talks of him as being one of the members of the "Legendary Party" - Descendents of Fianna (which is him and Orca) He and Orca are famous players in "The World" and achieved great status.
Balmung also plays an important role in the .hack video game storyline and the .hack//Legend of Twilight Bracelet series.
