The Balmung (バルムンク Barumunku, translated Balmunc in the Fire Emblem Museum and Balmunk in Fire Emblem Treasure) is one of twelve holy weapons from Fire Emblem: Genealogy of the Holy War. Balmung is the blade that was wielded by the Crusader Odo, and is the insignia representing the Kingdom of Isaach.
In Genealogy of the Holy War, only individuals possessing major Odo holy blood are able to wield the blade. Under normal circumstances, Shanan is the only character who can use the blade, though by using an exploit it is possible for Larcei and Ulster to be able to use the blade, provided that their mother has been paired up with Holyn.
After the conclusion of the Isaachian-Grannvaleian war, the Balmung blade is stored in the Yied Shrine. In Chapter 6, Patty/Daisy infiltrates the Yied Shrine and takes the Balmung blade. Just as she is about escape the shrine, Shanan, who has embarked on a mission to retrieve it, intercepts her. He then in convinces her to give the blade to him, explaining that he is the only one able to use it.
Balmung may have been named after Siegfried's (Sigurd) sword in the Nibelungenlied. This is a translation from the Norse myth, where Balmung is known as the Gram (Meaning 'wrath' in Old Norse), a sword that was wielded by Sigurd in order to slay the dragon Fafnir. It is called Nothung in Richard Wagner's Ring Cycle.
According to legend, Balmung was forged in the Wayland of Smith and originally belonged to Sigurd's father, Sigmund. The sword came into the hands of Sigmund in the hall of Volsung, after performing the feat of pulling it out of the tree Barnstokk into which Odin had thrust it, defying the belief that it could not be wrenched from its position. Balmung was later destroyed and reforged at least once, a fact that resulted in it possessing the ability to cleave an anvil in twain.
Interestingly, the Japanese romanisation for Siegfried's sword is almost always Balmunc (バルマンク Barumanku) instead of Balmung (バルマング Barumangu), the latter of which is the spelling that is utilised in-game. Along with many other examples of slight romanisation changes for character and weapon names, it would imply that Awakening's localisation of "Balmung" is actually erroneous, as it is the most common spelling for the weapon in English.
According to a conversation that can be viewed when visiting a certain village during the events that occur during the second generation of Genealogy of the Holy War, it is asserted that the Tyrfing, Balmung, and Mystletainn are the strongest blades to have ever been forged.