The Elder Edda and the Younger Edda/Elder Edda/The Slaughter of the Niflungs
Gunnar and Hogni then took all the gold, Fafnir's heritage. Dissension prevailed afterwards between the Giukungs and Atli. He charged them with being the cause of Brynhild's death. By way of reconciliation, it was agreed that they should give him Gudrun in marriage, to whom they administered an oblivious potion, before she would consent to espouse Atli. Atli had two sons, Erp and Eitil, but Svanhild was the daughter of Sigurd and Gudrun. King Atli invited Gunnar and Hogni to his residence, and sent to them Vingi, or Knefrod. Gudrun was aware of treachery, and sent them word in runes not to come; and to Hogni, as a token, she sent the ring Andvaranaut, in which she had tied some wolf's hair. Gunnar had sought the hand of Oddrun, Atli's sister, but did not obtain it. He then married Glaumvor, and Hogni took Kostbera to wife. Their sons were Solar, Snævar, and Giuki. When the Giukungs came to Atli, Gudrun besought his sons to intercede for their lives, but they would not. The heart of Hogni was cut out, and Gunnar was cast into a pen of serpents. He struck his harp and lulled the serpents, but an adder stung him to the liver.