The Dragon Fafnir & Siegfried
The story of Fafnir (also spelt Fafnar or Fafner), his brother Regin and the hero Siegfried is of Norse and Germanic origin.
Like many old stories, there are a large number different versions of the legend. This confusion probably hasn't been helped by the fact that Wagner used this story as the basis of his opera Siegfried, part of the Ring Cycle.
In some versions of the story Fafnir begins life as a dwarf, in others as the son of a human magician, in others even as a giant! There are many other variations, however the basic plot is as outlined below:
Fafnir and his brother Regin were sons of Hreidmar. Hreidmar received a large amount of gold - some say it was blood money for the death of another son, others that Hreidmar stole the gold.
Fafnir was greedy. Acting alone - or together with Regin according to version - Fafnir killed his father and stole the gold. He then refused to share it with his brother.
Fafnir then hid away, guarding his hoard jealously. His greed and the fact that he cared more for gold than humankind slowly turned him into a dragon. Some versions of the legend say Fafnir had no control over this change, others that he welcomed and encouraged it.
The hero Siegfried (also called Sigurd) heard of the dragon and Regin presuaded him to slay his brother and recover the gold.
In some versions, Regin tricks Siegfried and attempts to betray him, only to be himself slain by the hero.