Hreidmar

Hreidmar is a wealthy magician and farmer, father of Fafnir, Regin, and Otr. When Loki kills his son Otr, who liked to fish in the shape of an otter, Hreidmar seizes the three Aesir and demands wergild: enough red gold to cover the otter skin inside and out. Loki pays it with Andvari's hoard and the cursed ring Andvaranaut, which the dwarf curses to doom whoever owns it. Hreidmar gloats over his treasure but refuses to share, so his son Fafnir runs him through in the night and takes the gold, becoming a dragon to guard it. The curse claims its first victim at once.