The series is based on The Winter King, the first of Bernard Cornwell's Warlord Chronicles trilogy. Positioned as a revisionist adaptation of the Arthurian legend, The Winter King tells the story of Arthur Pendragon's rise from an outcast to a legendary warrior and leader. Set in the 5th century, long before the unification of Britain, the story takes place in a land full of hostile factions and tribes, where the world was cruel and life was often fleeting.