There are nine types of creatures that exist currently in the game, all but one of them are hostile towards "You".
ThinmanEditThe Thinman is first creature you encounter and the most abundant, and has 3 variants. Thinmen can be dispatched by using the Handgun or avoided entirely by luring them with Rotting Meat and hiding while they are drawn to its smell. They can be incapacitated with Flares. They are fairly perceptive, and will notice you if approach too close to them from behind or while feasting. They will always attempt to harm "You" whilst emiting a stark static noise upon detection and engagement.
The Type I Thinmen are found everywhere. They can endure up to 3 headshots before dying or can be shot in the knees by aiming low to make them stumble back. A good combination of attacks would be to shoot the knees, then the head, and repeat. Aside from being the first enemy the player encounters, they are otherwise unremarkable and are easily the least dangerous enemy in the game.
Type IIEditThe Type II Thinmen are found in Wing Court 2F (The first thinman you encounter), in the Wing Court 1F, The Basement and The City. They are slightly more resilient than Type I, and possess the ability to crawl along the ceiling in combat, and jump down. They will try to jump down behind you, becoming vulnerable only to a well placed upward shot from the Handgun. During this time, they are unable to harm the player until jumping down, which can be a good opportunity for the player to run past the monster without killing it.
Type IIIEditThe Type III roams The City and is almost identical to the Type II, with the only difference being that in addition to being able to climb ceilings, it also has the benefit of a ranged attack: when the player is within the range of a Type III Thinman, it can use its hands to spread open its face, revealing a cavity from which blood is propelled in a spray that harms the player majorly.
The Fatman is a monster first encountered in the basement, and found later in the city. They are daft, but can notice you if you try to hide behind them, and will walk towards you if you're near them. They will not notice you if you stand behind them. They are extremely tenacious, capable of enduring multiple gunshots until they fall to the ground. It is strongly advised to stun them by using Flares. Note that by stunning Fatmen, you force them into their "Helpless" form, which is considerably more aggressive and faster, and much more dangerous. The only way to get to another place by hiding is to trick them into thinking that you are in one place, then quickly run to the other area and get out, making them lose you.
They must face the flares to be affected by them, since they can't sense you with their backs turned. Flares alone are less effective than using a chain combination of Bullets + Flares. By doing this, you can take down hoards of enemies at once. Only shoot a Fatman when it is in its helpless state. Do not kill a helpless Fatman unless you have no concern for your mental health.
Upon being stunned or severely damaged, a Fatman falls to the ground and enters its second form. The "Helpless" Fatman, unlike what its name would suggest, is very much capable and is extremely perceptive, going so far as to spot and begin pursuing the player from couple a of screens away. In this form, they can still take up to 4 gunshots to be killed permanently. It is possible to run by them regardless of their attacks, though a group of "Helpless" Fatmen could potentially "stun-lock" the player. While in this form, they move faster and deal more damage. They are one of the monsters who wander behind the hospital, the place where you want the minor disturb possible, because in that place you can get the majority of the items you need to fight with the final boss: Mother. There you get the Wire Cutters and the Car Battery.
Writhing ThingEditFound in a room in the basement. It has no obvious function and is seemingly incapable of any action other than struggling. "You" finds it highly unsettling and is unable to discern anything about it.
It is the only pacific monster in the game. (So, he is pratically inutile, at least if you want to get the Blue Ending.)
In the Director's Cut shooting it will cause "You" to hallucinate a cave where he meets "Her", however it's strongly reccomended not to shoot it as it's really bad for your mental health. Shooting the writhing thing lowers your mental health by two ranks. (Example: Before shot MH, B-. After shot MH, C.)
The DoormanEdit"The Doorman" is a boss monster first found in Wing Court 1F when seen through a double door. It blocks the player from leaving the apartment complex and is seemingly invulnerable. Before you enter a room with "The Doorman", you must shut off your pocket flashlight, or you will die! It is later possible to summon a lift from the basement to trap it in, but "The Doorman" is able to escape by use of brute strength and relentlessly pursues "you" through the basement yet is unable to leave it and give further chase through a double door, supposedly due to its size.
It is able to catch up to you but while it is attacking you it will stand still giving you time to run away, so it can't get you if you keep on running.
The final boss monster of the game. When it appears, you will be trapped with it in a section of the street with two iron gate on each side, leaving no choice but to confront it. You can shoot it in the legs, in the midriff, or in the head, each having different effects on your overall Psych Report. Optionally, you can complete the fight without firing a single shot using Flares to distract it and running between its legs.
It has two attacks. With the first one it swings its scythes, and with the second one it slams them into the ground. It always screams and stands still before performing the second attack, and while it does this you can run between its legs to avoid it.
The creature is not killed upon defeat, rather it retreats and mortally wounds The Director.
'Her' EditAn infected version of 'Her' is the secret final boss of the "white ending" and as such can only be accessed in the Director's Cut version of the game, when playing New Game+.
'Her' is encountered in the hospital after you have amassed enough mental health to enter the first double door to the left. Her Ghost will appear in the very long corridor of the inner hospital. Once you see her and a short exposition, she will almost immediately crawl in your direction.
You will die instantly if touched by 'Her'. When attempting to shoot her, use flares, place meat, or turn on the flashlight, she will contort and distend her neck emitting a ghastly howl that will negate what You tried to do. The scream is comparable to a Thinman monster attack in damage. The only way to survive is to hide in the holes along the long corridor wall until she crawls past and immediately rush forward to the next hole. She will loop back constantly, and very quickly, continuing to approach You over and over again until You reaches the end of the area.
Nearing the end of the hallway there is a large horde of Thinmen obstructing the way, which 'Her' will crawl past. At this point, You must crawl past whilst hiding. When reaching the darkness past the Thinmen, 'Her' may continue to appear from the left.