Doors

What does he look like?
Dupe has a rather memorable and creepy appearance:

The face is white, with a wide, toothy grin. The teeth are bloodied, and the eyes are red and bloodshot. Both the smile and the eyes glow in the dark, making the monster especially noticeable in darkened rooms.
Most of its body is hidden in the darkness of the room where it resides. Only its hands are visible. They are dark black, skeletal-like, and each has five sharp fingers.
Sometimes you can see red spots on the face that resemble blood.
What is he doing?
Dupe appears in rooms with multiple doorways (such as large hotel rooms or mines). His gimmick is that he creates fake doors. These doors are marked with incorrect numbers—not the ones that follow the door the player entered through.

If the player makes a mistake and opens the fake door, the following will happen:

Human form: long, black, disheveled hair, red eyes, completely black skin, brown, torn clothes.

It's not a detailed elaboration, but a dark, almost faceless entity. It appears as a thick black shadow/mass, lacking clear facial features and a recognizable shape—it seems to "flow" or pulsate. When attacking, the silhouette becomes denser and more menacing.

What is he doing?
Hyde is responsible for the "time to sit under the bed/in the closet" mechanic. His mechanic is as follows:

Builds up "aggression" when the player runs around the room without cover for too long.
When the gauge is full, Hyde will throw the player out of the closet or under the bed and deal damage.
Essentially, it doesn't allow you to hide forever: the game forces you to move forward, rather than sit in cover forever.

Human form, dark red long hair, red skin, many eyes on the face, red jacket and black tie, brown trousers.

Glitch is a creature that is completely black and glitchy.

Human form: purple hair, black glitchy eyes, normal skin, black jacket, black pants. Everything lags.

A blue light that indicates the correct door or key in the room.

Human form: long blue hair, black skin with a slightly soft glow, a black and blue robe, a blue shirt, blue angel wings on the back, a blue moon pattern on the cheek, loose pants. A halo with blue stars above the head.

All monsters hate the guiding light.

This is an entity that appears in rooms: it doesn't attack directly, but deals damage if you look at it. It appears as a multitude of glowing eyes in the dark.

Human Form: Completely black skin, long purple hair tied in a loose ponytail, purple eyes all over the skin, purple bodysuit, black pants with a belt. Can talk in human form.
Jeff's best friend is friends with everyone.

Appearance
Jeff is almost completely hidden in the darkness—only a pair of large glowing eyes and dark blue tentacles (there are six of them) are visible. When the player buys something or gives a tip, Jeff's eyes turn blue and seem to "be happy." If you shine a flashlight on him, he will cover his eyes with a tentacle.

What does it do?
Runs a shop. In Jeff's room, there are four random items lying on the pillows (e.g., a lockpick, a flashlight, a cross, vitamins, etc.)—they can be purchased with gold.
Greets players. When you enter the room, Jeff waves his tentacle and waits for you to buy something.
He reacts to your actions. If you turn off his radio, he'll turn it back on automatically; if you fill his tip jar (with 100 gold), you'll earn an achievement, and Jeff will get a new jar.
Does not attack.

Human form: purple wrinkled shirt with a black tie, black gloves, black skin, black disheveled hair, purple eyes, purple tentacles behind his back, height 170.
Friends with everyone, best friend of the eye

Appearance: Orange hair tied in a bun, blue jacket, white shirt under the jacket, wide blue jeans, white skin.
Character: sometimes serious, but very cheerful, loves to joke, almost never takes anything seriously.

Appearance: brown curly hair, black jacket, blue T-shirt under the jacket, black jeans, white leather.

Character: Doesn't take things seriously, joker, loves to joke.

Appearance: Sik is an amorphous entity composed of a black, slime-like mass. He has no fixed form, assuming different shapes in different situations. Most often, during a chase, he appears as a humanoid made of black slime, with a single large eye instead of a face. His body and eyes emit a red light. In the "Dam" location, Sik appears in a different form: a huge, stationary blob of slime with multiple eyes, from which individual parts (arms, clots) emerge to attack.

Role in the game: Sik is one of the key enemy entities. In the Hotel, he appears as a secondary antagonist, and in the Mines, he becomes the main antagonist.

What it does:

He's watching the player. Before Sik appears, his eyes begin to appear on the walls in several rooms. This is a signal that the chase is imminent.
Initiates a chase. When the player reaches the end of a certain location (for example, the Grand Corridor in the Hotel or door 142 in the Mines), Seek emerges from the black slime on the floor and begins pursuing.
Creates obstacles. During the chase, the player must maneuver: duck to crawl under fallen furniture, search for the right exit in round rooms with multiple doors, and dodge flaming debris.

Human form: has a third eye on his forehead, normal skin color, black hoodie, black jeans, and messy black hair. Can talk in human form.
Figure's best friend

What does it look like?
The Figure is a tall, massive figure with distorted proportions, completely devoid of distinct facial features. The skin (or surface of the body) appears pale, almost waxy, and cracked in places. Its limbs are elongated and disproportionately long; its posture often appears unnaturally frozen. When the Figure is aggressive, a bright light flashes in its mouth—one of the character's most recognizable visual elements.

What does it do in the game?
Sensitive to sound and heartbeat, the figure is blind but possesses incredibly acute hearing: it reacts to footsteps, any noise, and even the player's increased heart rate if they get too close.
Patrols the room. It has a specific route around the room (usually room 50), and if the player gets in its way or makes noise, the Figure gives chase.
Roars and lights up its mouth. When the Figure hears something or is preparing to attack, it lets out a loud roar and its mouth lights up with a bright light—a signal to take immediate cover.
Pursues and kills on contact. If the Figure catches up with the player, they die.
It's related to a puzzle. In the room with the Figure, you need to collect books with images of figures and their numbers, and then, following the clue on the sheet, create a code for the lock on the door. This way, you can proceed further without directly confronting them.

Human form: light pink hair, light pink jacket with a black tie, normal skin tone, reading glasses, black pants, height 2 meters. Can talk in human form.
Sika's best friend

Ambush is a distorted, seemingly "glitchy" white face with exaggerated proportions. It has:

a monstrous oval mouth framed by several rows of internal teeth;
large, round, sunken, black eyes with grey-green bags under them;
green-orange aura (on a low chart it may look like a pink square aura).
What it does and how it behaves in the game
Spawns instead of Rush. There's a small chance that Ambush will spawn instead of Rush—the chance increases as you progress through the rooms. It can appear as early as the second door, but is more common towards the middle and end of the Hotel.
Doesn't flash lights. Unlike Rush, Ambush doesn't make lights flash: players only know he's there by a loud, distorted scream.
Makes multiple passes in a row. Ambush's main danger is that he doesn't just dash down a corridor once, but can run the same route 2-4 times (and more in some modes), returning back.

Human form: white skin, white hair with green streaks, black eyes, white shirt with a green tie, black pants.
Can talk in human form.
Rush and Scritch's best friend

Appearance: Screech resembles a grayish or pale pink floating ball covered in black, shiny slime. He has six tentacles surrounding his body, a creepy smile, and glowing white eyes. His design is partly inspired by the Ink Demon (from Bendy and the Ink Machine).

What it does:

Spawns in darkness. In "Hotel," Screech has a chance of spawning in naturally dark rooms (not those darkened by other entities like Rush or Ambush). But in "The Mines," he can spawn in almost any room, regardless of lighting.
He watches from afar. He doesn't immediately rush into attack: at first, he silently watches the player.
Gives signals. The player can suspect something is wrong by faint sounds (like light breathing) or a distinctive "Psst!" (Psst). Sometimes the screen vibrates slightly before appearing. This sound often occurs right before an attack.
Attacks if unnoticed. If the player doesn't have time to look around and make eye contact, Screech will startle the player (screamer) and bite them, which will take away about 40 health points (about a third).
Retreats upon eye contact. If the player sees Screech in time and looks directly at him, the jumpscare will still trigger, but the attack will not occur—the entity will retreat, screaming.
May reappear. The longer the player remains in the dark room, the higher the chance that Screech will reappear—rarely at first.

Human form: black fluffy hair, black hoodie, completely black skin, black pants, height 170, can talk in human form.
Ambush and Rush's best friend

What does it look like?
Rush is a black-and-gray, round creature, resembling a distorted moon. He has a huge grin and pure white teeth, and his eyes are black holes. During a jump scare, his mouth and eyes widen slightly.

What does he do in the game?
Appears when the doors are opened. Its approach is indicated by a flashing light for approximately 1.5–2 seconds.
Dashes through rooms. The rush starts a few rooms behind the player and quickly rushes forward. If the player gets in its way and doesn't take cover, it instantly kills them.
Breaks light sources. As it flies, it shatters lamps and other light fixtures. This causes rooms to become dark—and in the darkness, another entity, Screech, may appear.
Opens doors. Rush can open additional doors as he moves (but not all of them; for example, he can't open locked doors or special rooms like the library).
Reacts to cover. To survive, you need to hide in a closet, under a bed, or other cover before Rush reaches the room.
It depends on the number of people. The more people in a session, the slower the rush moves.
Human form: completely black skin, black jacket, black tousled hair, black cloak, white eyes, height 190 cm, black pants. Can speak in human form.
Abmush and Skritch's best friend