In each scene in which the murderer appears, their face is obscured by a black rubber mask with a ribbed hose attached running from the nose to the mouth. This mask is a breathing device the sanatorium used as part of the treatment for tuberculosis patients. The killer uses it as a tool both to instill terror in their victims and to conceal their identity. Interestingly, the doctors who tortured patients are pictured wearing the mask, suggesting that Cecile has now made herself into a villain rather than a victim.

Cecile also uses the black masks as a calling card, placing the masks over the faces of the victims before the bodies are found. The mask is used by the killer and her accomplice because of its connection to the sanatorium that was on the site of the hotel a century prior. For Cecile, using the masks was a way to create a stir about the hotel’s history and point out Lucas and Daniel’s callousness for not caring about the women’s treatment at the sanatorium. 

Cecile uses the copper bracelets to mark her victims. Each time before the killer strikes, the victim finds a copper bracelet nearby. Like the black masks, the copper bracelets are a remnant of the old sanatorium.