At the end of Wedding Horns, if you let Rued live during A Fury from the Sea, he will show up after escaping from captivity. At this point you’ll need to decide whether to let Oswald fight him, or if Eivor should fight him instead.
“Oswald, you can do this.”
If you encourage Oswald to fight Rued, you needn’t worry about him losing. This time he will win, and you will enjoy the sight of it. However, if Oswald fights Rued you will not be able to recruit Finnr as a crew member of your longship. Instead, Finnr will pledge himself to Oswald’s service after Oswald banishes Rued.
“Let me fight on your behalf.”
If you fight Rued rather than encourage Oswald to fight him, you’ll have an easy fight on your hands and it won’t be much of a show compared with what Oswald has to offer. However, Eivor fighting Rued will ensure that Finnr joins your crew. It will also seal the fate of Rued in death, rather than see him banished.