Living Corpse Reincarnation

The Living Corpse Reincarnation is jutsu that was developed by Orochimaru that allows him to transfer his soul to someone else's body. If periodically repeated, it grants the user immortality as long as they can find new host bodies and keep the host alive. Orochimaru can only perform this technique once every three years. It also seems that when the three years are almost over, he is forced to move into another host, as the previous one begins to reject him. Presumably, if he had a proper container, he could stay in the host for a full lifetime. The fact that he wants to prepare Sasuke Uchiha for the transfer before performing it seems to reinforce this.

To perform this technique, Orochimaru reveals his true form, a gigantic white snake composed of smaller white snakes, by abandoning his current host's body. Orochimaru then swallows the new host and takes him or her to a separate, mental plane where he envelops the mind of his victim. The snake body then dies and falls apart, and Orochimaru's soul dominates the body (though the Sharingan seems to be able to negate and reverse the process against Orochimaru). The souls of the hosts are kept alive within Orochimaru, leaving them "still alive", in a sense (albeit suppressed), and when Orochimaru switches hosts, the souls leave with him. Apparently if the host of these souls' chakra level falls enough it is possible for them to resurface in material form as seen with Orochimaru surfacing with his own body after Sasuke used up most of his chakra.

After taking over another body, Orochimaru modifies it to suit his theme of snakes, in order to increase his survival capabilities, such as stretching and bending his body and shedding his skin to heal injuries. This ensures that if Orochimaru cannot transfer body within the three years' time, he can allow it to greatly heal and evade attacks, rendering him virtually immortal. Orochimaru also alters the face of his host body to look like his original form.

While in this giant snake form, the smaller snakes that composes Orochimaru's body can extend themselves to strike and bind the targets. If Orochimaru is sliced to pieces, the body simply can reform, making him very difficult to kill. The blood that is released is also poisonous, evaporating into the air and paralysing anyone who has breathed it in.

Known host candidates

 * Itachi Uchiha (for the Sharingan; failed due to Orochimaru being unable to defeat him)
 * Unknown female (for replacing the hand Itachi Uchiha severed; left body after arms being disabled)
 * Kimimaro (for the Shikotsumyaku; rejected due to terminal disease)
 * Gen'yūmaru (a desperate temporary replacement body before Sasuke Uchiha; left body for Sasuke Uchiha)
 * Guren (for the Crystal Release; rejected due to being too late, anime only)
 * Sasuke Uchiha (for the Sharingan; failed due to being overpowered, then sealed away)