Orochimaru's Juinjutsu

Orochimaru's Juinjutsu are the cursed seals that were one of the most frequently-used technique of Orochimaru in the series, which he usually gave to his most powerful and unique followers. To apply a cursed seal, Orochimaru needed to bite his intended target. As he had sharp fangs and an extendible neck, this was a relatively simple task. The seal then appeared on the body of the victim near the point of application, and they subsequently lost consciousness. The design of the seals varied from person-to-person. Sometime later, had the victims survived, they would awaken with the first level of the seal active and be enraged due to the seal's influence. The seal grants the user access to additional chakra, giving the user a chakra capacity beyond what they would normally be capable of, as well as increased physical performance, especially in battle.

Overview
Orochimaru originally developed the cursed seals through experimentation on a boy named Jūgo, whose body naturally produces an enzyme that allows his body to passively absorb natural energy which triggers a bodily transformation, on which the cursed seal is based on. The difference between Orochimaru's seals and the unrefined enzyme are the effect that they have: while the cursed seal is controllable, the unrefined enzyme, extracted from Jūgo, produces uncontrollable rage and madness in those exposed to it, including Jūgo himself, and the effects cannot be controlled. Similarly, Jūgo is not limited to a single transformation, and can change the advantages of his form to fit the situation; while others would have their minds and bodies corroded by the seal, Jūgo is immune to such side-effects, due to being the main source of the enzymes. Also, anyone who survives the application of the cursed seal is "compatible" for Jūgo. This was shown when he was able to transplant some of his flesh to heal Sasuke.

It appears that the cursed seals are also partially made from Orochimaru's chakra. Kabuto stated that Anko Mitarashi was branded with one and contained some of Orochimaru's chakra inside her.

For the anime-exclusive seals, they tend to have fatal side effects if handled improperly, as seen when Mizuki's seal, which is unique in that it requires extra procedures to activate its powers, he nearly died due to using it earlier than he should, and lost all his powers regardless. The ones administrated onto Team Guren would kill them if they do not take the required medication periodically, which prevents them from escaping Orochimaru's clutches.

Mechanics
This transformed state forcefully absorbs the ambient natural energy into the user's body, similar to Sage Mode. It appears that the user must also possess an above-avarage chakra capacity in order to wield the curse seal's power. The key difference between the sage mode's voluntary and this involuntary absorption of natural energy is, however, that this forced transformation seemingly eats away at the user's body to sustain the state of absorption, as Anko noted, with possibly fatal consequences. As long as the user has sufficient chakra to sustain the state, he would then obtain additional chakra to perform skills he would been otherwise incapable of due to exhaustion. However, this absorbed chakra is separate and distinct from the user's own chakra, and ninjutsu generated whilst in second level transformation assumes a different colour. While the enhancements granted by the curse seals are noteworthy, they mostly pale in comparison to those of a full-fledged Sage Mode.

Because the seals forcibly draws chakra from the user, they will often kill the user when first applied. Orochimaru has averaged a ten-percent success rate when applying these seals based on his first experiment with his ten students, with only one survivor. Additionally, even if the user survives, their body will not be able to easily control the power of the seals given to them. To compensate for this, Orochimaru developed the Mind Awakening Pill. The drug forces the user's body to become accustomed to the unnatural increase in power, but also kills the one who takes it. The sealing technique Four Black Fog Battle Formation and Dark Sealing Method are used to keep the drug from killing the user by placing them in a temporary death state. Prolonged usage of the seals would corrode both the body and mind, making it easier for the users to be susceptible to Orochimaru's influence.

Transformations
The seal has two different levels, and the types of transformations differ from seal to seal. When inactive, the seal is simply a black tattoo on the user's body. Orochimaru has a wide array of cursed seals, so the appearance and power of the seal will usually vary from user to user. Each seal always has three identical marks arranged in a circular pattern. When first activated, 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. This is followed by an unnatural alteration of the user's body, with the only common features being yellow eyes with a black sclera, skin changing colour, and longer hair. When in this level, the seal eats away at the user's mind and personality, 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. Aside from the first and second levels of the seal, skilled users of the seal are able to perform partial transformations in which the aforementioned mutation caused to the user's body in the level two state can be used without altering the entire body. The power of the cursed seal can even synchronize with the user's regular body with extended use, increasing the stats of their normal state for a short time.

Cursed Seal of Heaven

 * Wearers: Sasuke Uchiha, Anko Mitarashi

Cursed Seal of Earth

 * Wearer: Kimimaro

Sound Four's Cursed Seals

 * Wearers: Jirōbō, Kidōmaru, Tayuya, Sakon and Ukon

Orochimaru's Prisoners

 * Wearers: Ahiko, Guren, Takishi, Tsukushi

Animal Cursed Seal (Anime only)

 * Wearer: Mizuki

Team Guren (Anime only)

 * Wearers: Nurari, Kihō, Kigiri