Þiðrekssaga
The Old Norse Þiðrekssaga (chapters 152-168) relates a slightly different tale, with Regin as the dragon and Mimir as Regin's brother and foster-father to Sigurd. In this version, King Sigmund returns home from travel and hears that his wife Sisibe has been accused of illicit relations with a thrall. Although the accusation is a lie told by two of his noblemen whose lustful advances Sisibe rejected, Sigmund believes it and orders the noblemen to take her into the forest and kill her. One is moved by pity for her, and the two fight. As they fight, Sisibe gives birth to a child (Sigmund's) and places it in a crystal vessel, which is kicked into a river and travels downstream. Sisibe dies; the vessel is found by a doe, which nurses the infant. Later, the young child is found by a wise smith of the forest, Mimir who names him Sigurd (although a few times the saga calls him Sigfred) and takes him as his own. When the child grows large and willful, Mimir asks his brother, Regin, a dragon, to kill Sigurd. But Sigurd slays the dragon and then kills his disloyal foster-father.
In chapters 225-230, Sigurd marries Gunnar's sister Grimhild, despite having promised to marry Brynhild. Later, Gunnar marries Brynhild, but she resists his attempts to consummate the marriage because she loves only Sigurd. As a favor to his brother-in-law, Sigurd sleeps with Brynhild, who is thereafter unable to resist Gunnar, as her strength came from her virginity.
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