Kriemhild

Gudrun is a major figure in early Germanic literature that is centred on the hero Sigurd, son of Sigmund. She appears as Kriemhild in the Nibelungenlied and as Gutrune in Wagner's Der Ring des Nibelungen.

In Norse mythology, Gudrun (Guðrún Gjúkadóttir) is the sister of king Gunnar. She falls in love with Sigurd, who does not care for her, as he is in love with the valkyrie Brynhild, to whom he once gave the ring of Andvaranaut. Gudrun's brother Gunnar also wished to marry Brynhild, but this was impossible as she had sworn to marry only the man who could defeat her in a fair fight, whom she knew to be Sigurd.

In another version of the myth, Brynhild is imprisoned inside a ring of fire as punishment by Odin. Sigurd fights his way through the fire and promises to marry Brynhild, but is then bewitched by the ring of Andvarinaut. Sigurd then switches bodies with Gunnar and, in this guise, gallops through the fire and wins Brynhild again, who is deceived by this ruse into marrying the real Gunnar. Gunnar had agreed to Sigurd's marrying Gudrun under the condition that Sigurd would win Brynhild for him first. When he was disguised as Gunnar, Sigurd also took the ring of Andvaranaut from Brynhild and gave it to Gudrun as his morning gift. Both queens, Gudrun and Brynhild, were married on the same day.

Gudrun's mother, Grimhild, called Ute in the Nibelungenlied, mixes a potion to make Sigurd forget his love for Brynhild.

Later, when Brynhild learns that she has been tricked into marrying the inferior Gunnar, she exacts vengeance by telling Gunnar that Sigurd had taken liberties with her, so Gunnar has Sigurd killed. Gudrun is so overcome with grief at the death of the one she loves that she cannot weep. The royal court fears for her life, and when finally her sister shows Sigurd's corpse to Gudrun, tears flow at last. Gudrun laments her lost husband and predicts the death of his killer, her own brother Gunnar.

...
Wikipedia