Ulf Bjalfason (Úlfr Bjálfason) (better known as Kveldulf, Old Norse for "Night Wolf") was a renowned hersir and landowner in ninth century Sogn, Norway.
He is a main character in the early chapters of Egils saga and appears in the Landnámabók and other Icelandic sources.
[1] Kveldulf was the son of Bjalfi and Hallbera Ulfsdóttir, daughter of Ulf the Brave and sister of Hallbjorn Halftroll.
When Thorolf was killed by King Harald's men, Kveldulf was overcome with grief and "took to his bed.
"[3] After having a request for compensation refused by the king, Kveldulf and his son Skalla-Grímr took revenge by killing Thorolf's killers before fleeing Norway for Iceland.