Orochimaru's cursed seals

Orochimaru's cursed seals were first developed through his experimentations on Jugo. Jugo's body naturally produces an enzyme that transforms the user into any number of different forms, drastically increasing their chakra supply in the process. By extracting this enzyme from Jugo's body and refining it, Orochimaru is able to apply it to whichever of his followers he wishes.

Once the cursed seal is applied, the applicant stands a 10% chance of survival and they lose consciousness as their body accepts or rejects the seal. Should they survive, receivers of the cursed seal are given access to the seal's first level. When activated the seal's unique pattern spreads across their body from the point of application; the more body coverage there is, the more the user is drawing upon the seal's effects. The seal forcibly draws chakra from the user's body and grants them with increased physical abilities, though consequently leaves them exhausted once the seal is deactivated. Their mind slowly corrodes while the seal is active, opening them to Orochimaru's influence and simultaneously advancing the seal to its second state.

Advancement to the second level of the cursed seal mark is a long process, so long in fact that Orochimaru developed a special drug to speed up the process. Once the second level is achieved, the user can enter the state by fully covering their body with the cursed seal. This is followed by an unnatural alteration of the user's body, with the only common features being yellow eyes with a black sclera. Aside from the first and second levels of the seal, skilled users of the seal are able to perform partial transformations in which level two state can be accessed without completely altering the entire body. The power of the cursed seal can even synchronize with the user's regular body with extended use, increasing the power of his/her natural state.