The story of Sigurd Fafnersbane
The dwarf Regins brother used to fish in the stream in the guise of an utter. One day Oden, Loke and Höner were out strolling around. They saw Utter who was feasting on a salmon. Loke killed Utter right away and thought it was extra fun to succeed in killing two creatures with one stone. At night the three of them arrived at someone´s house. It was suppertime and Loke gave his catch to the host. The host was, as it turned out, the dwarf Regin and his father Reidmar. Reidmar was not so pleased when he recognized his own son Utter on the dinner table. The dinner was quickly called off and Oden, Höner and Loke became prisoners and had to promise Reidmar to fill the empty otter skin with gold to get released. Loke was sent away to arrange this. He went to Ran, the sea god Aegir´s wife. Ran lures drowning men with a fishnet and keeps them with her at the bottom of the sea. Ran lent her fishnet to Loke who went to a certain stream where he knew a big treasure was kept. The golden treasure was watched carefully by a dwarf in the transformed shape of a big pike. Loke caught the dwarf and took the gold away from him. The dwarf warned him; the gold would only bring unhappiness to whoever stole it.
Loke gave Reidmar the treasure and they were thus free again, all three of them. The dwarf Regin had a brother, Fafne, who could also master the art of transformation. He took the shape of a snake (or dragon). He wanted to be the sole owner of the gold, so he took it and kept watch over it. Before that he made time to kill the present owner of the treasure, his father Reidmar. Regin told the story to Sigurd, his foster son. He then forged a sword to Sigurd because he wanted him to kill his evil brother Fafne. Sigurd did as he was told and together they roasted the heart of Fafne. Sigurd got some blood from the meat and suddenly he was able to understand the language of birds. A titmouse talked to him and warned him of the falsehood of Regin. He strongly recommended Sigurd to cut the head off his foster father and thus be the owner of the gold himself. Sigurd did again as he was told. He owned the treasure now but as it was prophesized it would only bring unhappiness. And sure enough, only bad things happened to him in later years.