The Izanagi is a Genjutsu that is cast on the user instead of others and is the most powerful amongst this type of Genjutsu.
Usage
When activated, the caster removes the boundaries between reality and illusion within their personal space. To a degree this allows the user to control their state of existence, but it is normally active for only the briefest of moments. At the same time, in the anime, a highly skilled user of this ability can expand Izanagi's range beyond one's personal reality, able to affect a large area and the people within it during the technique's activation.
Although the target remains physically real while fighting, this technique is capable of turning any occurrence including injuries and even death inflicted upon them, as long as the technique is active, into mere "illusions." Whenever the user receives a fatal injury, he or she will automatically fade away before returning back to reality; physically real and unscathed. The process is explained to have initially involved the administration of imagination, and the spiritual energy which forms the basis of Yin chakra to create shape and form from nothingness. Then, through the application of vitality, and the physical energy which forms the basis of Yang chakra to breathe life into the prior form.
Izanagi can be used only by those with the genetic traits of the Sage of Six Paths. The Uchiha, descended from the Sage, are able to perform Izanagi with their Sharingan. Even with such an eye acting as a medium, gaining the power to temporarily control reality's flow as the user sees fit comes at a price; one has very limited reserves of time within a single eye for invoking this technique. This technique would normally be used for only the most dire of situations and for but a brief moment as after the Sharingan with which Izanagi was cast exceeds its limit, the said eye becomes powerless and is rendered blind permanently, with the rare exception that its sight and power can be restored to the said eye by further evolving it into a Rinnegan. For this reason the Uchiha labelled it a Kinjutsu.
Danzō Shimura, in an effort to make practical use of the technique, had ten Sharingan embedded into his right arm. To use Izanagi to its full potential, users must also have the genetic traits of the Senju, who are also descended from the Sage. Partially for this reason Danzō had some of Hashirama Senju's DNA transplanted into his arm, which extended the time span of each Sharingan's Izanagi to a minute, allowing him to use the technique for up to ten minutes in total, with breaks in between to conserve time. However, because Danzō is not an Uchiha, his chakra levels drop substantially every time he activates this technique. Orochimaru would later perform a similar procedure on the Young Aroi Kraigen, but do to the Boys Uchiha and Uzumaki Ancestry, he was able to use them with far less Taxing requirements.
As with many Sharingan-based techniques, the Izanagi can be implanted into one's Sharingan to trigger the technique even after the user has already died; Madara demonstrated such usage after his actual death, as opposed to merely negating a mortal wound.