fafnir (fate)
The Fate depiction of the evil dragon from Germanic and Norse mythology. Depending on the story either Siegfried or Sigurd eventually slayed Fafnir, with it being possible that they both killed different versions of the same dragon.
Siegfried gained dragon traits after bathing in Fafnir's blood. After Sieg in turn obtained Siegfried's heart, he begins to be overwhelmed by the dragon blood, eventually fully changing into Fafnir's form.
He also appears as an enemy in Fate/Grand Order's Orleans Singularity.
