[1] It tells the story of Þorsteinn Þorvarðsson who stumbles upon a burial cairn and takes a sword from it.
The man, who wields a huge pole-axe, demands the return of the sword and threatens Þorsteinn.
The text survives in fragmentary form in AM 564a 4to[3][4] (Pseudo-Vatnshyrna) and in paper copies made by Árni Magnússon of the Vatnshyrna manuscript, which was destroyed in the Copenhagen Fire of 1728.
[5] Like Bergbúa þáttr, it is unusual amongst þættir for not being preserved as part of the kings' sagas manuscripts Flateyjarbók and Morkinskinna.
Stephen Mitchell considers Kumlbúa þáttr to be "a story that achieves neither a satisfying nor harmonious conclusion"[6] and one that communicates a message that "there are forces at loose in the world which cannot be countered, whose source of power is unclear, and whose design we do not understand.