In Norse mythology, Fáfnir was the dragon who had once been a dwarf corrupted by greed for gold.
Fáfnir appears in the Völsunga saga and in the Poetic Edda. After obtaining the cursed treasure of the dwarf Andvari, he killed his father, Hreiðmarr, and took the hoard for himself. His greed and fear transformed him into a monstrous dragon guarding the treasure.
The hero Sigurd kills Fáfnir by hiding in a pit and stabbing him from below as the dragon crawls over it. Fáfnir’s blood gives Sigurd the ability to understand birds, according to the saga tradition.
Fáfnir is often confused with Níðhöggr or Jörmungandr, but those are different Norse dragon-like beings. Fáfnir is especially notable because his story begins with a human character becoming a dragon.