In the Icelandic Hrómundar saga Gripssonar, a mighty berserker and sorcerer who conquered Valland (Gaul) and was king there. He had done much evil. He was so old that he no longer wanted to know adversity, so he retired into his barrow, taking with him his sword, armor, and much wealth.
Hrómundr, a servant of King Oláfr, went into the barrow and is there met by Þráinn, who challenges him to a fight. After a long match, interspersed with insults, Hrómundr defeats Þráinn, and the latter relinquishes his sword Mistilteinn. Hrómundr asks how many men he has killed in duels with the sword, and Þráinn answers that he has slain four hundred and twenty men, without ever being wounded. Among his victims was King Semin of Sweden. Hrómundr then kills the old man and cuts off his head.
It is also the name of a dwarf found in the catalog of dwarfs in Völuspá.
- Hrómundar saga Gripssonar, 3-4.