Devil

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Devils (悪魔, Akuma or デビル, Debiru) are a race of supernatural creatures that exist throughout the world. Some are extremely hostile and became hated enemies to humans and very seldom work with one another. The more human in appearance a devil becomes, the less animosity towards humans the devil in questions shows; most known are capable of communicating.

Overview
Devils are originated from Hell. When a Devil is born, it is given a name. The more that name is feared the more powerful the Devil is. If a Devil dies in Hell, they come to the human world. Once they die, Devils return to Hell. Thus they rotate in and out of these two worlds which effectively makes them immortal. According to Angel Devil, the only thing the Devils remember back from Hell is the sound of the Chainsaw Devil's engine roaring.

A variant of normal Devils are the Primal Devils. These are Devils that embody fears that are found naturally within the human psyche. Because of this, they are highly powerful and dangerous, having never experienced death nor been reincarnated on Earth. They are shown to cause immense fear amongst normal Devils and Fiends, including those who are seemingly unaware of their existence.

Abilities
Devils possess supernatural abilities which correlates with their name and unique to each other. They are able to restore their health by consuming blood from humans, fiends or other living creatures.

Devils are also capable of taking over a human's corpse, and turning them into a Fiend which are also possess supernatural abilities of a devil in a lesser degree.

Devils can make a contract with humans, providing them power in exchange for a sacrifice. A stronger devil requires a stronger contract, but if the devil likes it, people can sign a contract for a small price or borrow more power. These contracts are binding and once a devil and a human engaged, contract occurs. If any of them breaks the contract, it dies.

Hybrids
In rare cases, a devil can become fused with a human turning them into a hybrid which have human consciousness and appearance but can transform into a devil and manifest devil's abilities. There is no specific name because it has very few precedents, and it has only been rumored among Devil Hunters. It is later revealed that their specific name and origins were erased after being consumed by the Chainsaw Devil, though the Hybrids themselves continue to exist through unknown means.

Certain actions are triggers of hybrid transformation, with each action usually referencing a part of the devil a human is fused with (Ex. Denji transforms by pulling Pochita's tail like a Chainsaw start cord, Reze takes out a pin in her neck like a pin in a grenade). They are able to restore their health by consuming blood like devils and fiends. Their regenerative abilities are nigh-limitless and they can revive if there is an adequate amount of blood to consume. If there is not enough blood, the transformation will stop on the way even if they try to transform again, the armament will not appear even if you perform certain actions, or only the damage will recover and return to the human form. When transforming or disarming, the changed parts melt like mud.

There are eight known hybrids: Chainsaw, Katana, Bomb, Crossbow, Spear, Flamethrower, Broadsword, and Whip. Besides Chainsaw, others are collectively named as Weapon Devils (武器悪魔 Buki Akuma) and the Four Horsemen (四騎士, Yonkishi) by Makima.