Now comes the sad part of the Nibelung tale.
Brunhilda and Gunther invited Siegfried and Kriemhilda to visit them at Worms . During the visit the two queens quarreled and Brunhilda made Gunther angry with Siegfried. Hagen , too, began to hate Siegfried and wished to kill him.
But Siegfried could not be wounded except in one spot on which a falling leaf had rested when he bathed himself in the dragon's blood. Only Kriemhilda knew where this spot was. Hagen told her to sew a little silk cross upon Siegfried's dress to mark the spot, so that he might defend Siegfried in a fight.
No battle was fought, but Siegfried went hunting with Gunther and Hagen one day and they challenged him to race with them. He easily won, but after running he was hot and thirsty and knelt to drink at a spring. Then Hagen seized a spear and plunged it through the cross into the hero's body. Thus the treasure of the Nibelungs brought disaster to Siegfried.
Gunther and Hagen told Kriemhilda that robbers in the wood had slain her husband, but she could not be deceived.
Kriemhilda determined to take vengeance on the murderers of Siegfried, and so she would not leave Worms . There, too, stayed one thousand knights who had followed Siegfried from the Nibelung land.
Soon after Siegfried's death Kriemhilda begged her younger brother to bring the Nibelung treasure from the mountain cave to Worms .
When it arrived Kriemhilda gave gold and jewels to rich and poor in Burgundy , and Hagen feared that soon she would win the love of all the people and turn them against him. So, one day, he took the treasure and hid it in the Rhine . He hoped some day to enjoy it himself.
As Hagen now possessed the Nibelung treasure the name "Nibelungs" was given to him and his companions.