In both the Norse and continental Germanic tradition, Sigurd is portrayed as dying as the result of a quarrel between his wife (Gudrun/Kriemhild) and another woman, Brunhild, whom he has tricked into marrying the Burgundian king Gunnar/Gunther.
The Thidrekssaga finishes its tale of Sigurd by saying: [E]veryone said that no man now living or ever after would be born who would be equal to him in strength, courage, and in all sorts of courtesy, as well as in boldness and generosity that he had above all men, and that his name would never perish in the German tongue, and the same was true with the Norsemen.
[3] Although they do not share the same second element, it is clear that surviving Scandinavian written sources held Siegfried to be the continental version of the name they called Sigurd.
[10] Wolfgang Haubrichs suggests that the form Siegfried arose in the bilingual Frankish kingdom as a result of romance-language influence on an original name *Sigi-ward.
[18] Jens Haustein [de] (2005) argues that, while the story of Sigurd appears to have Merovingian resonances, no connection to any concrete historical figure or event is convincing.
[10][20] But the Sigurd/Siegfried figure, rather than being based on the Merovingian alone, may be a composite of additional historical personages, e.g., the "Caroliginian Sigifridus" alias Godfrid, Duke of Frisia (d. 855) according to Edward Fichtner (2015).
[21] Franz-Joseph Mone [de] (1830) had also believed Siegfried to be an amalgamation of several historical figures, and was the first to suggest a possible connection with the Germanic hero Arminius from the Roman period, famed for defeating Publius Quinctilius Varus's three legions at the Battle of the Teutoburg Forest in 9 AD.
When he is seen coming to Worms, capital of the Burgundian kingdom to woo the princess Kriemhild, however, the Burgundian vassal Hagen von Tronje narrates a different story of Siegfried's youth: according to Hagen, Siegfried was a wandering warrior (Middle High German recke) who won the hoard of the Nibelungen as well as the sword Balmung and a cloak of invisibility (Tarnkappe) that increases the wearer's strength twelve times.
He also tells an unrelated tale about how Siegfried killed a dragon, bathed in its blood, and thereby received skin as hard as horn that makes him invulnerable.
[58] The so-called "Heldenbuch-Prosa", first found in the 1480 Heldenbuch of Diebolt von Hanowe and afterwards contained in printings until 1590, is considered one of the most important attestations of a continued oral tradition outside of the Nibelungenlied, with many details agreeing with the Thidrekssaga.
Unattested in any other source, however, is that Kriemhild orchestrated the disaster at Etzel's court in order to avenge Siegfried being killed by Dietrich von Bern.
[62] The Icelandic Abbot Nicholaus of Thvera records that while travelling through Westphalia, he was shown the place where Sigurd slew the dragon (called Gnita-Heath in the Norse tradition) between two villages south of Paderborn.
[67] While some elements of the Scandinavian tradition may indeed be older than the surviving continental witnesses, a good deal seems to have been transformed by the context of the Christianization of Iceland and Scandinavia: the frequent appearance of the heathen gods gives the heroic stories the character of an epoch that is irrevocably over.
"[73] Sigurd is raised at the court of king Hjálprek, receives the sword Gram from the smith Regin, and slays the dragon Fafnir on Gnita-Heath by lying in a pit and stabbing it in the heart from underneath.
He says that Sigurd will go to the home of Heimer and betroth himself to Brynhild, but then at the court of King Gjuki he will receive a potion that will make him forget his promise and marry Gudrun.
[84] In Reginsmál, the smith Regin, who is staying at the court of Hjálprek, tells Sigurd of a hoard that the gods had had to assemble in order to compensate the family of Ótr, whom they had killed.
One day Regin tells Sigurd the story of a hoard guarded by the dragon Fafnir, which had been paid by Odin, Loki, and Hoenir for the death of Ótr.
[96] Sigurd then comes to the court of King Gjuki; queen Grimhild gives him a potion so that he forgets his promise to Brynhild and agrees to marry her daughter Gudrun.
[101] In the ballad Sivard Snarensvend (DgF 2, SMB 204, TSB E 49), Sigurd kills his stepfather and rides, with great difficulty, the unbroken horse Gram to his uncle in Bern.
[102] In the ballad Sivard og Brynild (DgF 3, TSB E 101), Sigurd wins Brynhild on the "glass mountain" and then gives her to his friend Hagen.
When Vidrek (Witege) doesn't believe Humlung and goes to check, Sigurd rips the oak tree from the ground and walks home with it on his back.
[107] There are a number of proposed or confirmed depictions of Sigurd's youthful adventures in Scandinavia and on the British Isles in areas under Norse influence or control.
[117][118] Four fragmentary crosses from the Isle of Man, from Kirk Andreas, Malew, Jurby, and Maughold depict Sigurd stabbing Fafnir from underneath.
[124] There is also a badly worn gravestone from York Minster that appears to show Regin after having been beheaded and Sigurd with his thumb in his mouth, along with possibly Grani, the fire, and the slain Fafnir.
[27] It is unclear whether Sigurd's descent from the god Odin via Völsung, described only in the Völsunga saga, represents an old common tradition, or whether it is a development unique to the Scandinavian material.
[131] Anglo-Saxon, Frankish, and other West Germanic royal genealogies often begin with Wodan or some other mythical ancestor such as Gaut, meaning that it is certainly possible that Sigurd's divine descent is an old tradition.
[131][132] Wolfgang Haubrichs notes that the genealogy of the Anglo-Saxon kings of Deira has a similar prevalence of names beginning with the element Sigi- and that the first ancestor listed is Wodan.
[72] Sigurd's liberation of a virgin woman, Brynhild/Brünhild, is only told in Scandinavian sources, but may be an original part of the oral tradition along with the slaying of the dragon, since the Nibelungenlied seems to indicate that Siegfried and Brünhild already know each other.
[146] It is possible that Siegfried's rescue of Kriemhild (rather than Brünhild) in the late-medieval Lied vom Hürnen Seyfrid reflects the tradition that Sigurd liberated a virgin.
[151] On the basis of the poem Atlakviða it is generally believed that Sigurd was not originally connected to the story of the destruction of the Burgundians by Attila (Old Norse Atli, Middle High German Etzel).