Fire Devil

The Fire Devil (の) is a Devil that embodies the fear of fire. They are the unseen overarching antagonist of the titular Justice Devil arc under the guise of the Justice Devil and as a major antagonist of the entire Academy Saga.

Appearance
The Fire Devil's true appearance is unknown.

Personality
Nothing is known about the Fire Devil's personality, except that their first few contracts tended to be with anyone who sees their actions as "right" and "justifiable" (such as the class president and Yuko) regardless of the actual morality behind their actions.

History
At some point the Fire Devil took up residence at Fourth East High School, beginning to make contracts with its students under the guise of the justice devil. It's unknown how many students they have previously contracted with, but one of them was the class president. The class president made a contract with the Fire Devil because she was jealous of her classmate, Asa Mitaka for capturing Mr. Tanaka's attention due to her aloofness, and the lack of socialization in their class. Mr. Tanaka was also having an affair with the class president, but it's unknown when it started.

Justice Devil arc
On her way to visit Bucky's memorial along with Mr. Tanaka and Asa, the class president uses her contract to transform into a being made of muscle and attempt to kill Asa. The class president is later killed along with Mr. Tanaka by the War Devil after taking Asa's body.

Later, Yuko also makes a contract with the Fire Devil, which allowed her to read Asa's mind. After being defeated by Chainsaw Man, Yuko later warns Asa that the Justice Devil is still at Fourth East High School, possibly having made contracts with other students.

Falling Devil arc
Following the Falling Devil's attack and the gradual rise of the Chainsaw Man Church, a person claiming to be Chainsaw Man appears during a press conference declaring that he has made a contract with the "Justice Devil".

Current Arc
It is revealed that essentially all members of the Chainsaw Man Church are or become contracted with the fire devil through a large-scale mass wedding event, at the cost of their humanity.

Abilities
As a Devil, the Fire Devil possesses all of the standard Devil abilities. These include the ability to make contracts with humans. The contracts with it seen so far are those with the class president, Yuko and the members of the Chainsaw Man Church (including the the Fake Chainsaw Man).

When passed off as the Justice Devil, the Fire Devil, unlike the other Devils, did not seem to ask for any price in exchange for their contract; Yuko tells Asa that the price for her contract is only to receive "a heart that shines with justice". Barem's words, however, imply that the price of the contract is one's humanity, with the contractors effectively being transformed into devils.

Devil Powers
Desire Granting: The Fire Devil's main power is that it can grant others the ability to transform depending on what they desire. As most people who made contracts with it were under the assumption that they were contracting the Justice Devil, many of their powers and forms reflect this. According to Barem, the forms taken by the contractors were initially more hideous and monstrous, but they later adapted to the wishes of the members of the Chainsaw Man Church.


 * The contract with the class president, who wished to have a happy ending with her teacher, gave her the power to transform her body into a blob of flesh with multiple heads, large muscular tentacles with claws-like fingers and superhuman strength. While in her transformed state, she is able to move very quickly, being able to attack in just seconds and she was capable to slice though Asa Mitaka's skull and flesh, killing her nearly instantly.
 * The contract with Yuko, who wished to punish the bullies who persecuted Asa Mitaka, gives her the ability to read others' minds and detect their inner thoughts and feelings. The contract also allows Yuko to transform into a thin and gaunt being with an uncovered brain and tentacles instead of legs.
 * The contract with a mysterious person, which gives him the ability to transform into a seemingly perfect copy of Chainsaw Man.
 * The contract with one of the Chainsaw Man Church elders gives him a warped figure with two heads, with one protruding on top of the other one. His view of Justice seems to be based on "fighting fire with fire," as well as the consequentialist rhetoric spread across the church.
 * The contract with numerous members of the Chainsaw Man Church, which allows them to transform into partial copies of Chainsaw Man. It is unknown if they currently possess a full devil form, but they can sprout chainsaws from their heads and arms.

Collective Empowerment: The Fire Devil has the ability to become more powerful based on the number of people who have contracted with it. According to Barem, the number of people who have contracted with the Fire Devil through the Chainsaw Man Church is currently 350.000.

Trivia

 * The Fire Devil's powers may be inspired by Robert Frost's poem Fire and Ice. According to the poet, fire represents human desires and ice represents hatred between humans. Desires are as hot as fire and can cause destruction by burning. Ice, at the opposite end of the spectrum, is cold, and so is how hatred can consume us if left unchecked.
 * Furthermore, the Fire Devil's power grows exactly like a fire that increases in intensity the more fuel there is (on which its collective empowerment power is based).