Rufinus gives Niall's enemy, Eochaid, a charm made by the witch Nemeta, a corded falcon skull with an arrow graven in the bone. She also cast spells.
There have been many forebodings that Niall's new expedition will be ill-fated and we have just been told how he will die. Eochaid and Rufinus join Niall's fleet. When it lands and makes camp, they go scouting, Eochaid carrying a bow and quiver. They see Niall. One arrow. That is all. This is just and is preferable to the slaughter that Niall would have unleashed.