Monsters are the main enemies in the Silent Hill series. They are horrid, visually terrifying creatures that are constantly trying to kill the protagonist and, sometimes, each other; although in some circumstances, they may not be hostile at all, such as the ghost children from Silent Hill. Claudia Wolf mentions that they have come to witness the rebirth of mankind and the arrival of the new paradise.
Monsters are created when a strong psyche's repressed thoughts are manifested by the power of the town of Silent Hill. Sometimes, the individual only needs to have a strong psyche powered by strong enough emotions or memories (such as trauma, sadness, fear, etc.) to manifest these monsters.
The nature and appearance of the monsters are linked to the individual that is experiencing the powers of the town. However, the exact nature and existence of the creatures is deliberately left to speculation. Such possibilities include that the monsters themselves, particularly the more humanoid ones, are actually sentient; damned souls trapped by the Otherworld, owing their violent and bizarre behavior to extreme psychosis, and their warped figures to the powers of Silent Hill, who use them against the still-living wandering its streets. It is interesting to note that if James Sunderland chooses to return to Vachss Road where he killed the first monster he encountered after leaving Brookhaven Hospital, the path is barred by a length of "Police Line - Do Not Cross" tape. Another possibility includes that the monsters themselves are in fact hallucinations that have no actual foundation outside the characters' minds. In one scene from Silent Hill 3, Vincent Smith suggests that they may be human beings that appear as grotesque monsters depending on the individual, but immediately says it is a joke to get under Heather Mason's skin. Whether or not he actually was joking is left up to the player.
Monsters are often very symbolic, due to the fact that they are manifested from the minds of a major character in the plot, whether it be the protagonist, antagonist, or other characters.
The monsters in the first entry are manifested from the repressed thoughts of Alessa Gillespie and her fears of her cruel classmates, adults and large dogs, added to her memories of her insect collection and hospitalization after her burning by her own mother. They manifest in two different dimensions, known as the Fog World and the Otherworld. The Air Screamer monsters were also inspired by Conan Doyle's The Lost World; one of Alessa's favorite books.
The creatures are made of living flesh and are bloody in appearance. They also take irregular forms that resemble insects and even humans.
The monsters in the second entry are from James Sunderland's repressed memories of the murder of his wife, Mary, his sexual anxiety and wish to be punished for his crimes; Angela Orosco's suffering due to years of sexual abuse from her own father; and Eddie Dombrowski's murderous thoughts towards everyone that mocked him in the past are all factors which helped to created new monsters and unique Otherworlds. The monsters in this case are all linked to sexual themes, as well as loneliness and guilt.
Heather Mason's thoughts and anxieties are to blame for the creatures in this entry, linking back to her hidden past as Alessa Gillespie. Although the monsters in the first half of the game are not manifested in Silent Hill itself, the Book of Lost Memories states Claudia Wolf's presence is the cause of the monsters and the Otherworld appearing.
It seems that in this installment, some human characters may be perceived as monsters, such as the Missionary, an Order Soldier who Heather sees as a monster due to Claudia's power, and Leonard Wolf, a deranged former Order member and Claudia's abusive father, who could be seen as a monster due to Heather's fear/disgust and/or Claudia's hate.
Walter Sullivan's memories of his orphanage's teachings and past fears are recreated as mutated and irregular creatures. Monstrous dogs are present once again, as are mutated humanoids, showing that Sullivan shared Alessa's fear of dogs and people. Past and present victims also are re-made as invincible ghosts (with the exception of the Twin Victims) in a more realistic Otherworld.
Many of the monsters in Silent Hill: Homecoming stem from Alex Shepherd's repressed guilt, feelings of being unwanted, and mental issues. Many of the monsters also pertain to a fate of Alex, or others, or how Alex perceives those around him in a subconscious state.
While these monsters are mostly derived from Alex's mind, four represent individual children in the town of Shepherd's Glen, who were murdered by their parents, with one exception having been killed by Alex himself. They take on twisted manifestations that are thematic to the way in which they were sacrificed.
It is interesting to note that every single monster seen in Homecoming has its own introductory cut-scene. This leads to suspense and while not a first, is definitely a departure from older games style of unveiling monsters.
The monsters in Silent Hill: Origins are partially created from Travis Grady's loneliness, sexual desires and guilt for running over animals with his truck, coupled with repressed memories about his parents. Again, Alessa Gillespie's fears appear as monsters as well, such as Caliban and Ariel, two characters from Shakespeare's The Tempest, which Alessa observed at the Artaud Theater.
Many of the monsters in The Arcade are recycled monsters used from previous titles, from Silent Hill 2 to Silent Hill 4: The Room. There are a few monsters that take on the appearance and characteristics of two monsters, which have been amalgamated to form as a hybrid. Due to the nature and pace of the game, many of the monsters are a lot more aggressive, with some displaying new forms of attacks. The majority of the bosses are unique, and possess connections to Hanna's projections in relation to her tragedy. This was also the first and only game to adopt Robbie as a form of aggressive enemy.
- Main article: Raw Shock
Raw Shocks are mirroring the thoughts of Cheryl Heather Mason. At the beginning, Raw Shocks are hairless, pale-skinned, humanoid creatures without facial features. Later there are 4 possible traits that the Raw Shocks may adopt based on Harry Mason's choices and personality. By the end of the game, it is possible to have 2 or 3 of these traits mixed together.
The monsters present in Silent Hill: Downpour reflect the criminal past and inner feelings of revenge and torment Murphy Pendleton and Anne Cunningham harbor. Murphy's vengeful feelings towards Napier for abusing and killing Murphy's only child manifests themselves with the Bogeyman and his experiences inside prison manifests themselves as monsters such as the Prisoner Minion and Prisoner Juggernaut. Other monsters revolve around the attacking of Frank Coleridge, such as the Wheelman which resembled a mutated body confined to a wheelchair, reflecting Frank's condition.
The monsters in Downpour all symbolize some form of vengeance or reference life in prison in some way, reflecting both Murphy's need for revenge against Napier for killing his son as well as Anne Cunningham's need to punish Murphy for mistakenly attacking her father.
In the film, Alessa Gillespie's thoughts are projected as gruesome monsters that represent either herself or people she knew. Pyramid Head also seems to have been created by the girl in this version, to punish the cult that burned her.