Fafnir

Fafnir is the son of Hreidmar and brother of Regin and Otr. When Loki's gold, the cursed hoard of Andvari, is paid to Hreidmar as wergild for Otr's death, Fafnir murders his own father to seize it, then turns himself into a vast serpent and coils upon the treasure on Gnita Heath, breathing poison. Regin sends his foster-son Sigurd to kill him; Sigurd digs a pit, waits beneath the dragon's path, and drives the sword Gram up through its belly. Dying, Fafnir warns Sigurd that the gold is cursed and will be his bane, then breathes his last over the hoard he murdered to keep.