Outer Path: Samsara of Transmigration Technique

The Outer Path: Samsara of Transmigration Technique is a heightened transformation unique to those who possess transmigrant status. It was first discovered by Ryun Uchiha and is the most powerful technique he can preform. According to Ryun, it is the single most powerful ability the Rinnegan can awaken, granted by the Rinnegan's Outer Path technique. The transformation itself is known as.

Appearance
While this mode is activated, the user's Rinnegan glow with intense light, losing its ripple-like pattern, as will the yin or yang markings on their palms. Occasionally, the user will also become enveloped in a similar bright aura. Additionally, in this mode, the user's voice is altered, overlapping with that of his previous lives, such as Ryun's overlapping with that of the voice of the transmigrant immediately proceeding him: Madara Uchiha.

Attributes
Similar to a jinchūriki transformation, this transformation allows the user to access both the chakra and the some of the abilities of their pasts lives. For instance, a transmigrant of Indra — the eldest son of Hagoromo Ōtsutsuki — could tap on and use the chakra of past, deceased Indra transmigrants, including that of Indra himself. The result is all of the transmigrants focusing their chakra and knowledge into a singular body (that of the user), heightening the user's speed, strength, and defenses. The enhancements afforded by this transformation are comparable to that of a jinchūriki's own transformation. In this form, the user is capable of using all six techniques of the Six Paths Technique in tandem with each other.

While transformed, the user gains the knowledge of their past lives, allowing them greater proficiency with their techniques. An example of this is when Ryun used this Mode subconsciously to fend off Seireitou Hyūga shortly after awakening his Rinnegan; reflexively using the Deva Path due to Madara's knowledge of the Six Paths Technique. During the same battle, he demonstrated this feature once more by learning from Indra how to completely stabilize his Susanoo against Seireitou. During yet another one of their battles, the specters of Ryun's past lives manifested themselves during a tremendous release of chakra, shocking Seireitou who was temporarily able to see them with his Byakugan.

Under normal circumstances, the user can willingly enter and exit the Samsara Mode simply by focusing chakra into their Rinnegan. However, as demonstrated by Ryun, situations of intense emotional upheaval, or in times of great peril, the transformation will activate subconsciously. This can be dangerous because the intense emotions ruling the transmigrant can cause them to fly into a rage, destroying everything in sight until they run out of chakra, inadvertently killing themselves.

Drawbacks
This transformation does come with several significant risks. In order to use the abilities and chakra of one of their past lives, the user must exchange their own chakra equal to the amount they intend to use. As a result, the chakra strain of this technique is significant. The transformation also requires that the user keep steady command of their chakra, as losing control of the tremendous power of this form can cause catastrophic damage to their own body. There also exists a single technique capable of countering the user while transformed. By preforming the Release: Demonic Sealing Formula technique while the user is in this mode, the opponent can tear out and seal the souls of the user's past lives — albeit only one at a time — and seal them away, significantly weakening the user. Should all of the user's past lives be sealed, the transformation will end, and they will die.

Trivia

 * This technique is heavily based on the "Avatar State" from the Avatar animated series.
 * This technique was created as a retcon for Ryun Uchiha's jinchūriki abilities in the Fanon Canon. As such, only the Fanon Canon version of Ryun knows how to preform this technique, making it non-canon to Ryun's official storyline.