King Horik is based on the historical figure of Horik Gudfredsson, who was a Danish king at the onset of the viking age. The character is played by actor Donal Logue.
In Season 2, his story is expanded on as he has more dealings with Ragnar. However he is a manipulative man who turns Jarl Borg against Ragnar and ultimately this leads to Ragnar turning against King Horik.
(Photo Credit: History Channel, Metro-Goldwyn-Mayer Studios Inc.)