“It took your music… your WORDS to make me realize she was the filth in my life. The filth that had to be cleansed!”
Mark Cida, known better as “Acid”, was responsible for six murders in Silent Hill during the late 90s. He put his victims into their own bathtubs, filled with acid, until the skin would eat away to their vital organs. He was able to sedate victims prior to their dip by pumping the room full of gas. It is unknown how he met his end in life, though it is hinted he fell into a vat of his own acid.
Acid is a victim of child abuse from his mother. Not surprisingly, his mother became his first victim. He had a lonely childhood which most likely contributed to his demented mental state.
During Silent Hill: Resurrection
Acid encounters Royce Keller and the others in an industrial area of Silent Hill. He doesn’t directly confront the group at first and seems to focus his attention on Royce. Through several clues and the manner of the masked man’s murders, Royce figures out Acid was the one who murdered his mother.
Eventually, Acid traps the group on a platform suspended by chains over acid in a processing plant. He reveals Royce’s music inspired him to commit his murders, relating to the anguish expressed in the song that Royce expressed toward his own mother. Acid offers Royce a way out of Silent Hill and feels betrayed when Royce refuses. After a battle, Acid is knocked into the acid below where the banishing circle lies. Using Royce’s CD, the group activates the circle and destroys the killer known as Acid.
While not lacking in the strength area, Acid prefers the use of dangerous chemicals. He shoots the vile liquids out of a long nozzle, which is connected by a tube to the tank on his back. His expertise with his equipment gives him the ability to use his tools quicker, making him quite a dangerous opponent.