Fáfnir

Sources relate that the gold-hoard at the centre of Fáfnir's story originates as weregild paid to Hreiðmarr after the gods (Odin, Loki, and Hœnir) caused the death of Ótr. Andvari the dwarf provided gold including the ring Andvaranaut, which was cursed. Fáfnir kills his father Hreiðmarr to seize the hoard, refuses to share it with his brother Regin, and withdraws to the wild where he 'shifts into the hamr' of a worm/dragon to guard the treasure.

Medieval sources vary. Earlier poetic accounts (Fáfnismál) describe Fáfnir in his transformed state as a flightless, snake-like 'worm' (Old Norse: ormr). Later prose (Völsunga saga) adds shoulders to his description, a development under continental influence that suggests a more dragon-like form (interpreted in some traditions as implying limbs or wings). The pre-transformation appearance is not consistently described in the sources; some texts identify kin who elsewhere have dwarf associations, but Fáfnir's precise human or dwarf visage before metamorphosis is not explicitly fixed in the surviving material.

Narrative attestations show Fáfnir's principal behaviours as acquisitive and guarded: he murders for a hoard, withdraws into wilderness to brood over it, patrols between lair and water (leaving a track), and emits 'atter' (poemically rendered as poisonous or venomous exhalation). He functions as a hostile, treasure-guarding creature slain by a hero; the canonical method of his death is an ambush in which Sigurð hides in a trench across Fáfnir's path and stabs through the belly into the heart. Sources do not ascribe other specific supernatural faculties beyond these narrative elements.