Gauk
Foster-brother of Asgrim, slain by him, whose death became a lasting reproach, attested in 1 source.
Gauk Trandil's son was the foster-brother of Asgrim, described as "the fairest man of his day, and best skilled in all things" (Njal's Saga, Chapter 26). The relationship ended in violence: Asgrim slew his own foster-brother (Njal's Saga, Chapter 26). This act became a point of lasting reproach. At a later confrontation, Asgrim's slaying of Gauk was thrown in his face as a counterweight to other men's great deeds -- set alongside Gizur the White's overcoming of Gunnar of Lithend -- to suggest that Asgrim's most notable accomplishment was the killing of someone bound to him by the closest ties (Njal's Saga, Chapter 138).
Both attestations come from Njal's Saga but serve different narrative purposes. The initial account in Chapter 26 establishes the facts baldly: Gauk was Asgrim's foster-brother, he was exceptional in appearance and skill, and Asgrim killed him. The saga offers no explanation for the killing, letting the bare statement carry its own weight. The second reference, in Chapter 138, transforms the killing into a rhetorical weapon. An adversary deploys it in a public exchange meant to diminish Asgrim, pairing the foster-brother slaying with Gizur's triumph over Gunnar to imply that Asgrim's reputation rests on a shameful act rather than a heroic one (Njal's Saga, Chapter 138).
Appears in: Beings, Entities in Njál's Saga, Norse Tradition
On trail: Genealogies