Question: who plays the wanderer in vikings season 3
Answer: Alexander Ludwig as Bjorn Ironside , Ragnar and Lagertha 's son , who has fallen in love with the shieldmaiden Þórunn Alyssa Sutherland as Queen Aslaug , Brynhildr 's daughter and Ragnar 's second wife Ben Robson as Kalf , the ruler of Hedeby in the absence of Lagertha Kevin Durand as Harbard , a wanderer Lothaire Bluteau as Emperor Charles of West Francia .