Sigurd and Fáfnir
As told by Norse oral tradition
There were once three brothers, Otr, Fáfnir, and Regin, sons of a magician. Otr could turn himself into an otter, and one day, in his otter shape, he was killed by Loki, who did not know it was a man. As ransom, Loki was forced to fill the otter's skin with gold and cover it. The hoard he took came from a dwarf named Andvari, who cursed it as it was taken from him. Whoever owned the gold, the dwarf said, would die for it.
After their father had been paid, Fáfnir killed him for the hoard. He drove Regin out and went to a wild heath, lay down on the gold, and over the years he changed. He grew long and scaled. He grew wings and breath of poison. He became a dragon, lying in the grass with his belly on the gold. The hoard was his and no one could take it from him.
Regin, the brother who was driven out, became a smith in the hall of King Hjálprek. There he raised a young man named Sigurd, son of Sigmund of the line of the Völsungs. Sigurd was strong and clear-eyed and quick to learn. Regin saw what kind of man Sigurd would become and laid his plan.
He told Sigurd about the gold. He told him about Fáfnir, his brother who lay on it now in dragon shape. He said: "Take this gold. It is owed to me. Avenge my father's blood. The hoard is yours if you can take it."
Regin made a sword for Sigurd, and Sigurd broke it across the anvil. He made another, and Sigurd broke that too. At last Sigurd took the broken pieces of his father Sigmund's old sword, Gram, which his mother had kept. Regin reforged it. The new Gram cut the anvil itself in two, and Sigurd held it and was satisfied.
Sigurd rode out to the heath where Fáfnir's track ran down to a stream. The track was a long furrow worn in the earth where the dragon dragged himself daily to drink. Sigurd dug a pit in the path and lay down in it, with Gram pointed up.
The dragon came over the hill, dragging his belly along the ground. He passed over the pit. As his soft underbelly went over Sigurd, Sigurd drove the sword up through it, into the heart, and held it there as the great body shuddered and the venom sprayed and Fáfnir spoke his last words.
"Whoever you are who has killed me, the gold will kill you too. The curse is on it. Take it if you wish."
Sigurd climbed out of the pit. Regin came up. "Cut out his heart," Regin said, "and roast it for me, and I will eat it."
Sigurd built a fire and put the heart on a spit. As it cooked he reached out to feel if it was done, and he burned his thumb. He put the thumb in his mouth to cool it. The dragon's blood touched his tongue.
In an instant he understood the speech of birds. The little birds in the bushes overhead were arguing.
"Sigurd is roasting Fáfnir's heart, and Regin will eat it. Then Regin will know everything Fáfnir knew."
"Sigurd would do better to eat it himself."
"Sigurd would do better still to kill Regin first, before Regin kills him. Regin is planning it."
Sigurd took out his sword and cut off Regin's head where he was sleeping by the fire. Then he ate the heart of Fáfnir himself.
He gathered the gold onto the back of his horse Grani. The hoard was so heavy that no other horse could have carried it; Grani had been chosen by Odin himself. Sigurd rode away with the gold, and with him rode the curse the dwarf had laid on it. He did not know yet what shape the curse would take. He had a long way to go before he met the woman in the ring of fire on the mountain, and before he made the oaths he would later break, and before the gold killed him too. But that morning he was the dragon-slayer, and he rode away into the rest of his life.