The Crow (fellow Demon) Several past contractors Ellen's Predecessor (former contractor) Ellen (current contractor)
Role in Story
In Game
Used as the game's save point; revives the player after encountering a "Game Over" screen
In the Book
Makes a pact with Ellen to grant her powers,the House, and the status of Witch; Guides Ellen throughout her reign in the Witch's House; Gives Ellen the body switching spell and lures Viola to her house.
Status
In Game
Leaves host body and the Witch's House; Watches 'Viola' exiting the Witch's Forest with her father in the 'Good Ending'; Vanishes along with a presumably deceased Viola in the True Ending
In the Book
Accompanies Ellen (now in a new body) to confront Viola in the Witch's House
"By the way, this is a witch's house, but you already knew that, right?"
―The Black Cat to the player
The Demon ( 悪魔, Akuma), more commonly known as the Black Cat (黒猫, Kuroneko), is an unnamed talking cat to whom Viola talks in order to save the game. True to their contract, the Black Cat will reset time in case anything happens to Ellen until he can fulfill his contract with her. If the game is completed without saves, you get a Secret Ending. The ending itself does not change anything story wise, but it gives you far more information than the other two endings, revealing and explaining more backstory. It officially reveals that the cat was actually a demon with whom Ellen had a contract, from which her powers originated. In exchange for more souls, I will tell you a spell that cures your sickness. The cat holds a contract with Ellen, and this is further explained in the novel.
The Black Cat seems perpetually neutral about the abnormal situation in which the player participates. His only motive is to ensure that the contract is fulfilled. Sometimes he even cracks jokes, mentioning that he's following the player "for laughs", perhaps because he knows the player will win no matter what, rather than that he finds their deaths or struggles amusing. Although he seems quite cruel, he mentions how it was mean of you to kill the white flower, though this could be a mere ironic jest. He also seems genuinely worried about the player sometimes, telling them it wasn't a smart idea to come into the house. As a demon, he is true to his contract and will protect it no matter what, which may make him quite reliable.
He also mentions his liking for a cat's body, which he uses as his form on earth since demons do not have true forms.
"Cats are just so elegant. I quite like a black cat's body."
"It'll be a pity when you're gone. Pretty cat bodies like these ain't just lyin' around."
The demon leaving his host body. The scattered purple streams is his true form.
In his host body, the demon takes the appearance of a black cat with golden eyes.In that form, Ellen describe's his voice to be that of a young boy.
In his true demonic form, however, he is actually a ghostly purple haze.
History
After Ellen had brutally stabbed her parents to death and burned the house down, the demon ate their souls and tied a contract with Ellen, promising to cure her incurable disease in exchange for offering him countless souls. He then offered her a house with magic, which she will use to her advantage to kill off countless "friends", offering their souls to the demon.
"The witch's house devours humans. Their souls are offered to a demon.
The witch's house is purposeful. If any spirits residing in it remain unfed to the demon, that purpose is unfulfilled.
The witch's house is magic, granted to a witch by a demon."
The witch's house (3), (4), and (5), explaining the purpose of a witch's house.
Though it wasn't enough to fulfill their initial contract, she found a way to switch bodies. Changing their plans, Ellen "befriends" Viola and slowly builds up a strong bond in order to obtain her body. The Cat will follow you throughout the game, allowing you to save your progress in case anything were to happen. Near the end however, in two endings you can see his dead body laying before Ellen's room. When you step on it, it makes a squishy noise like blood. This is explained by him in the Secret Ending: it is because he knows the witch will die soon, and when the witch dies, so does the house and everything in it. He had left the black cat's body, before he would perish with the house. He also explains how demons do not have forms, but that does not mean they're immortal. At the very ending, he reappears in his cat form only to vanish with the witch's body once again.
Powers and abilities
Just as all demons differ in their preference for animal hosts, they also differ in the power they specialize in.
Master Illusionist: The Black Cat specializes in spells that focus on deception and instilling fear into his targets, something that is clearly reflected in the traps lurking within the Witch's House. He himself claims that he prefers such spells because he finds that souls of humans who die in agony "are tastier that way". Some of these spells involve making people see illusions, peering into a person's heart, controlling a person's body, and many others. The spell for the House and the effect it has on Ellen's outer physique might arguably be included in that category of spells.
The set of jutting spikes before (left) and after (right) getting killed.
Temporal and spatial manipulation: The Demon is able to reject and negate any kind of event that has happened to a target. This ability is seen both in the game (if the player chooses to save on the Black Cat) and novella, where he returns an injured or 'killed' Ellen to her former healthier state, no matter what has happened to her. A famous in-game example is found in the Correct Mouth Pathway, where a set of spikes is placed near the door to the fourth floor. The spikes are purposely placed out of the player's path, making them very easy to avoid. However, if the player willingly chooses to have Ellen (in Viola's body) walk over them, she will be impaled to death, triggering the 'Game Over' screen. If the player loads the game using the exact same file and come back to that same room, the set of spikes will surprisingly be smeared in blood, hinting that 'Viola' did indeed 'die' and was somehow brought back to life. Another in-game example is in Extra mode, if you read the Funny Story you will be shot, if you load the same save file and go back there you will see that there is blood on the floor where you have been shot.
Teleportation: The Demon is capable of teleporting himself and his target to different locations.
