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 among 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.

Another ability common among all Devils is the ability of revival: when a Devil dies, they are revived in hell. This ability makes them practically immortal. However, once they are killed in one dimension, their memories and personalities are reset. Thus, each incarnation of a devil is completely different people, as shown with Makima and Nayuta. However, their appearances or quirks can have similarities.

Contracts
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 engage, a contract occurs. If any of them breaks the contract, it dies.

Fiends
Devils are capable of taking over a human's corpse and turning into a Fiend. The personality of the fiend may mirror that of the corpse if the brain is still intact, as evident by the Violence Fiend's polite and gentle attitude. In these scenarios, the devil may also retain some memories from the body they took over.

Fiends are less powerful than their devil counterparts and are able to use toned-down versions of their respective supernatural abilities. They can regenerate from drinking blood, but unlike hybrids, they can die if fatally wounded.

Hybrids
In rare cases, a human can become fused with a devil and turn into a Hybrid. This can be occurred via a contract. Hybrids have human consciousness and appearance, but can transform into a human-devil hybrid and manifest the supernatural abilities of the fused devil. The official name for hybrids was erased by the Chainsaw Devil, and hybrids continue to exist despite their erasure for unknown reasons.

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, Longsword, and Whip. Besides Chainsaw, the others are collectively named as Weapon Humans (武器人間 Buki Ningen) by Makima.