Aside from leads Nick Cheung Ka Fai and Daniel Wu (Ng Yin Cho), THAT DEMON WITHIN (MOR GAING) by The Emperor Motion Pictures also had veteran actors like Liu Kai Chi, Au Kam Tong, Leung Cheuk Moon and Lee Kwok Lun who played robbers and "ghost king gang" members, adding a lot more colors to the film.
According to a report on Hktopten, one of the fighting scenes was cruel and bloody, almost earning the film a category III rating.
In order to add mystery to the "ghost king gang". Director Dante Lam Chiu Yin arranged for them to work in a funeral home. For example, Au Kam Tong was the usher, Lee Kwok Lun made paper offerings, Leung Cheuk Moon made floral arrangements, and Liu Kai Chi was the agent who was responsible for the accounting.
In the end, Nick Cheung's character caused them to turn on each other as they began to suspect each other.
In one scene, the "ghost king gang" members suspected that someone had leaked information and thus, ran over the traitor's arm during interrogation. For realism, the team prepared a big basket of pig blood and ground meat to simulate the run-over arm.
Uncle Chi recalled that on first night of the shoot, the Ma On Shan location was filled with the stench of blood. He still has chills from it even now.
In the film, Lee Kwok Lun was stabbed with a screw while in a struggle with Uncle Chi. The film also had other scenes that people might think have crossed the line.
Lam Chiu Yin also admitted that he thought the film would be rated Category III at first. It finally only received a IIB rating.
"Actually THAT DEMON WITHIN doesn't have anything to worry about whether or not it is rated Category III. However, if I knew in advance that it would be rated Category III, I would have gone even further during the shoot and wouldn't had to adjust."