Skodi Skeggvason cut off Ullveig Helgasdottir's hair after defeating her in combat. Shamed by this, Ullveig vowed not to grow her hair back until Skodi is dead.
Ullveig later erected a nithing pole (with one of the Skeggvarshold draft horses chopped-off heads on top!) declaring that she wouldn't marry or regrow her hair until Skodi was dead.
Ullveig later ambushed Skodi, got her ass kicked again, and was taken prisoner by the Skeggvasons; after some negotiations and Skodi magically reattaching her hair and rings, she "escaped" and has declared the feud over.
The Skeggvarsons have thrice thwarted Droskar, the evil god of the gray dvergr (or the duergar, as they are called in Common). They slew his forge-spurned and freed the innocent souls it had forged into its chain; they revealed and helped destroy the Droskar Cult among the dvergr Rune Guild in Orkafjall; and they protected Svirkr Firetongue, former leader of the Droskar Cult, as he atoned for his heresy by slowly killing himself in the Teeth of Torag.
This is not exactly a feud, but presumably Droskar is not going to take this lying down. On the other hand, it's not clear what if anything he can do in the surface world – his worshippers largely live in Svartalfheim.
After a yellow musk zombie of one of their relatives showed up in Feyjasfjord, Hallgrimm and company have renewed the feud with Gudrun and, by extension, Skeggvarshold. Hallgrimm blames Gudrun for not properly burning his slain relatives after she killed them twenty years ago. He brought suit against her, but in her absence her son Skodi spoke for her. Hallgrimm produced a mysteriously convenient lawspeaker named Kavlax who oversaw the trial. Here it was settled that Gull-Skeggi and his family and Hallgrimm and his family would take the recently returned longship the Blood Star on a viking expedition, that Gull-Skeggi and Skodi Skeggvarson would donate their shares of the mission to Hallgrimm, and that would settle the debt.
However, Hallgrimm apparently just used this as a pretext to wreak vengeance on the family of Gudrun: on the first night at sea, he drugged or slew Gull-Skeggi and his part of the crew and abandoned them on Kalva – on the same beach where, many years ago, Gudrun had slain his relatives and left their unburned corpses. He left a smoky fire burning to summon the cannibalistic inhabitants of the island to a feast. His daughter Ullveig, while she did not stop the betrayal, felt that Gorum would not approve of leaving the Skeggvarsons unarmed, so she smuggled their weapons ashore, evidently against the will of Hallgrimm.
Gull-Skeggi suspects that Hallgrimm is taking the Blood Star back to Feyjasfjord to attack Gudrun at Skeggvarshold; he turned into a seagull, and flew off to her aid.
Skodi Skeggvarson has sworn that he will kill Hallgrimm and his entire household, with the exception of Ullveig and the thralls.
The "Hallgrimm part" of the crew of the Blood Star was:
|Hallgrimm||A powerful priest of Gorum|
|Ullveig Helgasdottir||A fighter; Hallgrimm's daughter|
|Skapti the Lame||An adept; Hallgrimm's son|
|Kvann Hallgrimmson||A ranger; Hallgrimm's son|
|Old Meg||A waves oracle; Hallgrimm's sister|
|Yark Nefnirsson||A half-orc fighter; Hallgrimm's nephew|
|Grizur||A roguish human pal of Hallgrimm|
And a couple of thralls. This group includes pretty much all of the warriors of any fame who live in Hallgrimmshold, although he has another ten or so who can lift an axe but are of no particular repute, some of whom are thralls.