Regin
;)
and his brother Fafnir slew their father, the magician Hreidmar, while under the spell of a cursed ring, Andvarinaut, which made them covet their father's gold. While Fafnir turned into a dragon in order to protect his gold, Regin settled down as a smith in the royal Danish household. There he tutored the young hero Sigurd and urged him to overcome Fafnir, which he did. But, equally as corrupted by the curse as his brother, Regin then plotted to murder Sigurd. However, he reckoned without the young hero's insight: Sigurd was forewarned by the birds and killed Regin first.