One day, Fasti came upon Geirmund Hel-hide while collecting oysters for food. Geirmund introduced himself and asked whether there was room at the fire for him, as he was alone and hungry, having just washing ashore after jumping into the stormy North Sea to allay his longship crew's superstitions.
Fasti gave Geirmund the basket of oysters for him to carry and lead him to their camp at Ancarig, where the Danes had stationed themselves waiting to see if the anchorite Torthred could die twice, believing he was a living-dead creature. They ate, and a short time later that night, Fasti surprised Geirmund as he stole one of their boats. Fasti drew breath to shout an alarm, but Geirmund plunged his knife in Fasti's throat before he could cry out, killing him.
After Halfdan Ragnarsson learned of Fasti's murder, he demanded either weregild of eighteen pounds or Geirmund's death in compensation. His commander Krok decided to hunt the Hel-hides and their leader, believing it would be enough to have Halfdan make him a jarl, but the Hel-hides provoked him into a prolonged chase for many miles, during which they eliminated his hunting party one by one. Krok was ultimately by Geirmund in a holmgang witnessed by Eivor Varinsdottir.