Whom the Gods Wish to Destroy (1966)

Siegfried of Xanten snatches the Nibelung treasure from the king of the underworld and slays the dragon Fafnir, whose blood makes him invulnerable. Siegfried falls in love with Kriemhild, the sister of the Burgundian king. But only if Siegfried helps Gunther marry Brunhild will he be allowed to marry Kriemhild. He fulfills this condition, but the two women bring ruin upon Xanten and Burgundy...