Lord Siegfried Rookwood is the head of House Rookwood, one of the most powerful vassal families of House Blackthorne. His father was Amadeus Rookwood and his mother was Barbrey Mannister; he had an older twin brother Sigmund who was heir-apparent to the lordship until his death during a tourney accident thanks to Valus Thormund. Talia Blackthorne, who Siegfried's twin lusted after, thinks the younger brother to be a more sullen, spiteful and combative creature than the chivalrous elder. Siegfried has a grudge against Valus and will take any opportunity to offend or upset the Thormund family. He is a grim, pale-faced youth with braided dark hair and grey eyes. He wears a suit of black-and-orange plate in battle and carries a longsword.

With the death of his father at the Fourth Battle for Nchurdamz, Siegfried has ascended to the role of Lord. He is councilled in all matters by his mother, much to his chagrin, as he sits on Lord Dominic's councils.