Hybrid

Hybrids (real name unknown) are humans who have the ability to take on the form of a Devil.

Overview
In rare cases, a human can become fused with a devil and turn into a hybrid. The only known method of becoming a hybrid is done via a contract. Hybrids have human consciousness and appearance, but can transform into a human-devil hybrids and manifest the supernatural abilities of their fused devils. The official name for hybrids was erased by the Chainsaw Devil, and hybrids continue to exist despite their erasure for unknown reasons. They are indistinguishable from regular humans unlike fiends while they are not transformed into devils.

There are eight known hybrids: Chainsaw, Katana, Bomb, Crossbow, Spear (槍 Yari), Flamethrower (火炎放射器 Kaen hōsha-ki), Longsword (長剣 Chōken), and Whip (鞭 Muchi). Besides Chainsaw, the others are collectively named as Weapon Humans (武器人間 Buki Ningen) and were members of Special Division 5 under the supervision of Makima.

Hybrids usually remain in their human form when not transformed, but they can also turn back to their Devil form under special conditions, as seen when Denji fully transform into Chainsaw Devil, the condition for this to happen is still unclear.

Abilities
The main ability of a hybrid is transformation into their respective devil forms fused with their human form. Certain actions act as triggers for 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). Their strength, speed and durability is increased dramatically after the transformation and they also gain the ability of their respective Devil. Their transformation usually effects their heads and arms, but skilled hybrids can also transform their legs into weapons.

They are able to restore their health by consuming blood, like devils and fiends. However, their regenerative abilities are nigh-limitless and they can revive if there is an adequate amount of blood to consume, even if their head is severed or their heart is removed from their body. 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.

Like regular humans, and unlike fiends, hybrids can make contracts with devils, as it is shown that despite having a contract with Pochita, Denji is also able to contract with Blood Devil. However, it is unknown that this actually was a contract or just a verbal agreement between friends, as Power was a fiend.