The Parasite is a mysterious mind-controlling monster that makes its only appearance in the first Silent Hill game.
It infects the entire staff of Alchemilla Hospital (with the exception of Michael Kaufmann), the Puppet Nurses and Puppet Doctors as well as Cybil Bennett. There is also speculation that it infected Lisa Garland.
It seems to be weak to Aglaophotis, which is shown to completely reverse the parasite's effects on Puppet Cybil Bennett. It is also implied that Aglaophotis is also made from White Claudia, suggesting White Claudia may be the ingredient which attacks the parasite. PTV is produced from White Claudia as well, which may be the reason Lisa didn't transform as soon as her co-workers, if she was infected.
The slug-like Parasite is about half a meter in length. It is a reddish-brown color.
Victims of the parasite often vomit blood and bleed from their head and every orifice. They also tend to have hunchbacks. At one point, Lisa seems to exhibit involuntary twitching of her left eye, although this is only relevant if Lisa was infected.
Not much about the Parasite's meaning is known, but along with the other monsters, they are likely to be connected to Alessa Gillespie. They may be related to the God's fetus in Alessa's womb, as the God can be seen as a parasite to Alessa's body, nourishing off her hatred and fear. It also might represent Alessa's feelings of how the Order is manipulating her life, given their ability to control other living things.
- A similar creature in appearance are the Tremers of Silent Hill 4: The Room. It is possible that they may be the same creature, especially considering Henry Townshend can be mildly injured by merely contacting one.