According to the Orkneyinga Saga, in the war which followed, Thorfinn defeated Karl in a sea-battle off Deerness at the east end of the Orkney Mainland.
Finally, a great battle at Tarbat Ness on the south side of the Dornoch Firth ended with Karl defeated and fugitive or dead.
The Saga, when dealing with Thorfinn's childhood, mentions a brother named "Hvelp or Hundi" who was taken to Norway by King Olaf Trygvasson and died there.
[11] Woolf proposes that Karl Hundason, rather that being some hitherto unknown Scots king, was the son of Thorfinn's brother Hlodver Hundi.
[13] Muir (2005) points out that a literal translation of "Karl Hundisson" is "peasant son-of-a-dog", an insult that may have been obvious to Norse-speakers hearing the saga and that "we can assume this wasn't his real name".