In an interview with Timid Magazine, the narrative reasoning for Wang Wei's muteness comes from an incident in China that left him with a metal plate in his skull, forcing him into exile as a tradesman. A brief sequence indicating this back story is shown in the mainland China and Hong Kong released version, re-cut by the distributor Edko Films. By stripping the character of the ability to speak, yell, or grunt during his combat scenes, the filmmakers created a striking contrast between his silent intensity and the aggressive shouting of his enemies.
Brian Le (Ho) based his fighting style on Donkey Kong from the Super Smash Bros. video games.
Joe Taslim (Navin) is a non-smoker but smoked real cigarettes to be in line with the character's exhaustive investigation.
The decision to make Xie Miao's character (Wang Wei) mute was an intentional creative choice to channel his emotional frustration inward rather than outward. Director Kenji Tanigaki and Xie designed this limitation to emphasize the character's internal power, showing his intense paternal drive and rage completely through his physicality, facial expressions, and brutal martial arts.
During filming, Xie Miao (Wang Wei) experienced high blood pressure and was hospitalized for a few hours for IV treatment. He resumed filming immediately after his discharge.
