Orochimaru's Juinjutsu

These cursed seals are created and utilised by Orochimaru.

Overview
Lacking a body strong enough to handle Sage Mode, Orochimaru had to create an alternative method of utilising senjutsu. Orochimaru thus used Jūgo, whose body naturally produces an enzyme that triggers bodily transformations, to develop a brand of cursed seals that would feed off the wielder's chakra while supplying them with Orochimaru's senjutsu chakra. As a result, those compatible with the cursed seals are also compatible with Jūgo, allowing him to transplant his own flesh and chakra into their bodies.

In addition to his various test subjects, Orochimaru gave cursed seals to some of his most powerful and unique followers, either to enhance their abilities or to prepare them for becoming potential host bodies. To apply a cursed seal, Orochimaru bites the recipient, doing so with the aid of his sharp fangs and extendible neck. The seal then appears on the body of the victim near the puncture wound before causing them to lose consciousness. If the victim survives the application of the seal, they subsequently awaken with its first state activated. Orochimaru has created a wide array of cursed seals, so the appearance and power of the seals vary, with all known variations comprising of three identical marks arranged in a circular pattern.

As the cursed seals are created with Orochimaru's senjutsu chakra, they also contain portions of his consciousness. When the seal is combined with a piece of his DNA and the Evil Releasing Method is performed, Orochimaru can be completely resurrected, even if his body was destroyed or sealed.

Removing a cursed seal is not impossible, but requires very difficult methods to accomplish, so much so that even Kakashi Hatake opted to use the Evil Sealing Method to suppress the one on Sasuke Uchiha's body, as he did not know anyway of removing the seal without damaging Sasuke's body at the time. Itachi Uchiha only succeeded in removing Sasuke's cursed seal by the Sword of Totsuka when he removed Orochimaru's emerging form from Sasuke's body. Sasuke later used the Evil Releasing Method, along with a piece of Orochimaru's DNA source, to remove the seal on Anko's body, albeit this actually manifested a new body for Orochimaru's lingering consciousness, instead of simply removing it.

Besides his transformation-inducing cursed seals, Orochimaru can use a binding seal to restrain victims. Applied through the same neck biting as his other seals, the binding seal spreads across the victim's body, immobilising them. Unlike the other cursed seals, however, the binding seal is not permanent and recedes after a few moments.

The anime-exclusive cursed seals tend to have fatal side effects if handled improperly, as seen when Mizuki's seal, which was more of a failed prototype that required extra procedures to activate its powers, nearly killed him due to its incompleteness and caused him to lose all his powers. The cursed seals administrated to Team Guren would kill them if they do not take the required medication periodically, preventing them from escaping Orochimaru's clutches. On the other hand, the seals given to the Iburi clan partially stabilised their otherwise unstable ability.

Mechanics
When activated, the cursed seal releases Orochimaru's own senjutsu chakra into the user's body, granting enhancements comparable to those of Sage Mode. The seal eats away at the user's own chakra to sustain its activated state, as Anko Mitarashi noted, with possibly fatal consequences. As long as the user has sufficient chakra to sustain the state, he or she would then obtain additional chakra to perform skills they would have otherwise been incapable of due to exhaustion. However, this additional chakra is separate and distinct from the user's own chakra, altering their chakra signature. Prolonged usage of the cursed seal can corrode both the body and mind of the user due to Orochimaru's chakra being present, making them more susceptible to his influence.

Not all individuals are compatible with these cursed seals, with incompatibility resulting in death. Orochimaru has averaged a ten percent success rate when applying these seals based on his first experiment with ten test subjects, out of which Anko was the sole survivor. Even if the individual survives the initial application, their body will not easily be able to control the seal's power, resulting in intense pain. When the user is unable to control or otherwise suppress their cursed seal, it can forcibly activate and begin draining their chakra whenever they attempt to manipulate it. To compensate for this, Orochimaru developed the Mind Awakening Pill, a drug which forces the user's cursed seal to advance to its second state, though doing so will result in the user's death. The Four Black Fogs Formation and Dark Sealing Method are used to keep the process from killing the user by placing them in a temporary death state. The power of the cursed seal can synchronise with the user's regular body through extended use, exponentially enhancing the abilities of their normal state.

Transformations
The seals have two different levels, and the types of transformations differ from seal to seal. When inactive, the seal is simply a black mark on the user's body. Upon activation, the marks on the seal glow and replicate, spreading over the user's body. This is known as the of the seal. The degree to which this occurs is dependent on the user, and the degree to which it spreads is proportionate to the overall effect it has. Normally, the wearer of the seal will also experience slight pains during the activation of this level.

The of the seal causes the black marks to completely envelop the user, followed by many unnatural alterations to their body. Once transformed, common features include eyes with yellow irises and black sclerae, altered skin colour, and longer hair. When in this state, the seal also eats away at the mind and personality of its user, driving them to madness if used for too long. It also takes quite a toll on their body, since they are being mutated by the seal. Skilled users of the cursed seal are able to perform partial transformations in which the aforementioned alterations can be limited to specific parts of the body.

Whereas Jūgo's ability is known as Sage Transformation, the transformations induced by these seals are called.

Types of Seals

 * Cursed Seal of Heaven: Worn by Sasuke Uchiha and Anko Mitarashi.
 * Cursed Seal of Earth: Worn by Kimimaro.
 * Sound Four's Cursed Seals: Worn by Jirōbō, Kidōmaru, Tayuya, Sakon and Ukon.
 * Prisoners' Cursed Seals: Worn by Ahiko, Guren, Takishi and Tsukushi.
 * Binding Cursed Seal: Worn by Tobi.

Anime-only Seals

 * Animal Cursed Seal: Worn by Mizuki.
 * Team Guren's Cursed Seals: Worn by Nurari, Kihō and Kigiri.
 * Iburi Clan's Cursed Seals: Worn by Gotta and Yukimi.