"The powerful one." A son of Hreiðmarr, and the younger brother of Fáfnir and Ótr. He was the most skillful of men, and a dwarf in stature; he was wise, cruel, and versed in magic. After the death of Ótr at the hands of Loki, the Æsir paid Hreiðmarr a large amount of gold in recompense. Fáfnir and Reginn demand their share of the gold, but Hreiðmarr refused, whereupon Fáfnir slew him in his sleep. Reginn then requested to have his share of the patrimony, but met with refusal from Fáfnir. Reginn thereupon sought council of his sister Lyngheiðr, and she advised him to demand his share of the patrimony with the sword. Fáfnir departed with the treasure and went to Gnitaheið, where he transformed himself into a serpent or dragon.
Reginn went to king Hjálprekr and there became the king's smith. He took into fostering Sigurðr, and told him about how Fáfnir lay on Gnitaheid. He forged a sword for Sigurðr, that was named Gramr, and after that instigated Sigurðr to slay Fáfnir. Sigurðr first avenged the death of his father, and then went with Reginn to Gnitaheid. He dug a pit in Fáfnir's way and lay himself in ambush therein. When Fáfnir slid towards the water and came above the pit, Sigurðr thrust his sword through him and the serpent died.
After Fafnir's death, Reginn cut out his brother's heart with his sword and drank the blood from the wound. He told Sigurðr to roast the dragon's heart for him to eat, and then settled himself for sleep. While Sigurðr was roasting the heart, he checked with his finger to see if it was fully cooked. He burned his finger, and put it in his mouth. As the blood from the heart touched his tongue, he suddenly understood the speech of birds. The nuthatches told him that Reginn planned to betray him, so he grabbed his sword and cut off Reginn's head. Sigurðr then ate the heart, and drank the blood of both Fáfnir and Reginn.
The name also appears as that of a dwarf in the catalog in Völuspá.
- Skáldskaparmál, 40.
- Völsunga saga, 13-19.