Susanoo

Susanoo, also known as the, is the third ability granted by the Mangekyō Sharingan after awakening the abilities in both eyes. It creates a gigantic, humanoid being that surrounds the user. As the strongest technique granted to those that have acquired the Mangekyō Sharingan, it is the user's guardian deity, but at the same time, it consumes the user's life.

Overview
According to Tobi, for a Sharingan user to activate the Susanoo is a rarity. Like the other techniques granted by the Mangekyō Sharingan, the user's eyes and body are strained while using Susanoo because it consumes a large amount of their chakra. Sasuke described it as feeling pain in every cell in his body which only grew from prolonged use. Susanoo is formed through the materialisation of the user's chakra and as such differs in appearance as well as colour between users.

Despite Susanoo's impressive defensive capabilities, the protection it grants its user is not absolute. Even though it envelopes the user, they can exit it freely or even use techniques from inside of it, but also that the user can be thrown out of the upper half of Susanoo by manipulating the substance under their feet. This was seen when Gaara used sand to pull Madara out of his Susanoo. Also, a sufficiently powerful attack will still result in damage, especially during the technique's developmental stages. The only known ways to attack the user while Susanoo is active, is either to draw the wielder out of the technique and then attack, bind and restrict its movements, or to break the defence with overwhelming force. Susanoo users are also vulnerable to attacks which don't actually deal physical damage to it, such as strong lights and sounds, that can also impair their ability to sustain Susanoo. Sound-based genjutsu can also bypass Susanoo's impressive defense.

Development
Each Susanoo goes through several different forms, which the user can switch between at will or even leave in a state between forms. The development of these forms was best demonstrated while Sasuke was learning how to use the technique, gaining additional forms as his control over it increased. In its earliest form, users can only manifest some of Susanoo's skeleton. A smaller version of Susanoo's ribcage is generally produced first which, while providing a good defence, can still be fractured, or even melted. An arm can also be formed, which is sometimes connected to this ribcage, and can then be used to interact with the surroundings. It is also possible to utilize one of Susanoo's weapons using said arm and change its size as needed. When first forming, Susanoo manifests around the user like an aura.

As users gain additional control, musculature and skin begins to appear atop of its bones, which progressively complete the full skeletal structure. It is only when Susanoo's growth is fully matured and thus, the user is completely surrounded, are the vulnerabilities of the skeletal form finally eliminated. However, it should be noted that Susanoo can also appear behind the user, instead of just surrounding them. The user can also change the size of it to fit the current situation. Eventually, Susanoo develops into a "complete" warrior-like form, where its skin, armour and final arsenal of weapons are manifested in their entirety. At this stage, it can anchor the user to the ground, preventing opponents from forcibly moving them unless they can get through Susanoo's various layers. In its final form, this fully humanoid shape is further surrounded by a secondary layer of armour that causes Susanoo to resemble a yamabushi.

Itachi's Version
Itachi's Susanoo is yellow in the manga, while it was depticed as red in the anime. Of all the known Susanoo, Itachi's looks the most humanoid. When seen in its complete form, it has a normal face with what resembles locks of hair framing it. The only odditty that Itachi's Susanoo displays is an appendage on its chin reminiscent of a Pharaoh's false beard. When in its final form, the armour that surrounds Itachi's Susanoo resembles a long-nosed tengu which wears a pair of magatama earrings. Its right hands also gain plating on it giving the hand the appearance of "peeling". In addition to its secondary right hand, Itachi's Susanoo has been depicted with a secondary left hand while in its incomplete form. Itachi has also displayed the ability to manifest parts of Susanoo such as its ribcage or hands as the situation calls for.

In its left hand, Itachi's Susanoo wields the Yata Mirror, a shield which is endowed with all nature transformations, allowing it to change its own characteristics depending on the the attack it receives, thus nullifying it. In its right hand it wields the Sword of Totsuka. The sword is a variant of the Sword of Kusanagi, also known as the, and is sheathed in a sake jar held by the third hand growing from Susanoo's right forearm. It is an ethereal weapon with an enchanted blade capable of sealing anyone it pierces. Victims of the sword are trapped in a genjutsu-like "world of drunken dreams" for all eternity. Zetsu said that the Totsuka Sword combined with the Yata Mirror essentially makes Susanoo invincible.

For longer-ranged attacks, it is able to use the powerful Yasaka Magatama, which can be used as three chakra tomoe bound together by a single, circular thread and fired as a projectile or several tomoe strung out on a chakra string which detach themselves and fire off individually. It is also able to utilize a weapon resembling a curved dagger while in its incomplete form.

Sasuke's Version
Sasuke's Susanoo is violet in the manga, while it is depicted as purple in the anime. In its incomplete stage, his Susanoo possesses a sword and in its complete stage it possesses a bow that doubles as a weapon and shield. It is able to produce chakra arrows to use with the bow via an orb held by its third hand, which can be fired at such speed that evading them is nearly impossible. It can also use the arrows as a makeshift melee weapon. In its final stage, Susanoo's orb changes into the black flames of Amaterasu, which Sasuke is able to manipulate into various forms using Blaze Release: Kagutsuchi, and its bow grows in size and takes on a more shield-like appearance. Sasuke is able to switch between these weapons regardless of which stage Susanoo is in.

Sasuke's development of Susanoo is marked by intense feelings of hatred; whenever angered by the words or actions of his opponents, Susanoo grows in power. His Susanoo is, accordingly, noted to be much darker in composition compared to Itachi's Susanoo. In both its incomplete and complete forms, it has a more demonic appearance in contrast to Itachi's, which have a more "normal" human-like appearance, possessing horns, a long appendage on its chin and a malevolent grin. In its final form, it also possesses jagged teeth around its hood (unlike Itachi's which features straight teeth) and magatama earrings. In addition to its secondary right hand, Sasuke's Susanoo has been depicted with a secondary left hand while in its incomplete form.

After Sasuke gains the Eternal Mangekyō Sharingan, the second layer of armour changes its appearance. The mouth of the armour changes to a beak shape, giving it an even more menacing look. The skin on the right arm and right hand gains additional platings that gives the appearance of the skin peeling off and the armour itself becomes more ghastly in appearance. The orb is now made entirely of the flames of Amaterasu and the arrows are at least seemingly coated with the flames, as seen when one of them pierced White Zetsu and set him ablaze. Sasuke can also throw the flames in a tomoe shape, setting his foes on fire.

Madara's Version
One of the first two amongst the Uchiha to awaken the Mangekyō Sharingan, Madara awoke a Susanoo of his own after awakening the abilities in both of his eyes and is also able to use it while having his Rinnegan activated.

Unseen in others' versions, Madara's Susanoo demonstrates an entire body including a lower half and legs, which are visible when it leaves the ground, and two entirely different sides that are conjoined along their spine, each with a distinct pair of arms and a unique face. One of these faces has elongated canine teeth in its upper jaw bracket and a single horn protruding from its forehead. The other has similarly elongated canine teeth in its lower jaw bracket instead, as well as two tusks growing from this jaw.

The right hand of each side wields an undulating blade and the Susanoo itself appears to be capable of contributing towards some of Madara's techniques, as it was seen forming hand seals when he drew down two meteorites. It is also able to use the powerful Yasaka Magatama, creating a string of magatama in its attack.

Influence

 * Similar to other Mangekyō Sharingan abilities, Susanoo was taken from Japanese mythology. Susanoo, the god of sea and storms, was the brother of Amaterasu and Tsukuyomi, with Susanoo born from Izanagi washing his nose.
 * Susanoo's designs are based on, well known yokai that are associated with the ascetic practice of shugendō. In their final forms, both Sasuke and Itachi's incarnations of Susanoo are garbed in the attire of shugendō practioners, known as yamabushi, and wear hoods that resemble tengu masks, with Itachi's appearing as a long-nosed hanataka tengu and Sasuke's as a crow-billed karasu tengu. Susanoo-no-Mikoto is said to have been the progenitor of the tengu.
 * The is the sword used by Izanagi to kill his newborn son, Kagu-Tsuchi, after his birth burned his mother, Izanami, to death. From the blood of the Totsuka no Tsurugi, eight new Shinto gods were born. The same sword is later used by the god Susanoo to slay the eight-headed and eight-tailed snake, Yamata no Orochi, just like it was used by Itachi's Susanoo to defeat Orochimaru's.
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Trivia

 * In the anime, the final form of Sasuke's Susanoo has few minor changes: aside from having five fingers instead of six, and having straight teeth, it was also shown wielding a gourd in the secondary right hand instead of an orb, making it look similar to Itachi's final Susanoo.
 * Itachi and Sasuke's Susanoo are depicted a different colour in the anime than the manga. This is due to the fact that their Susanoo were illustrated in the anime before being coloured in the manga.
 * Prior to the completion of Sasuke's Susanoo, it was glimpsed as a shadowy figure in a genjutsu that Sasuke placed C under.
 * Both Itachi's and Sasuke's final form of Susanoo's mouth area always appear to face to the right but the mouth area of Sasuke's new version faces to the left side instead.
 * Sasuke's bow-wielding form of Susanoo bears a great resemblance to Raideen the Brave, one of a number of Yoshiyuki Tomino references in the series (another being the Gundam-derived names of Kakuzu's techniques).
 * The Totsuka Sword wielded by Itachi's Susanoo is considered to be a "Sword of Kusanagi", although this has been popularly mistranslated as it being the perfect counter to the Sword of Kusanagi.
 * During the Sasuke vs. Itachi boss battle in Naruto Shippūden: Ultimate Ninja Storm 2, Susanoo doesn't appear around Itachi, but behind him. However, during his "awakening", Susanoo appears around him in a much smaller form.
 * When it was first shown, Itachi's Susanoo had five fingers on its hands. Recently however, instead of five, it has a total of six fingers per hand, like all other known Susanoo.
 * Both Itachi and Sasuke's Susanoo were illustrated earlier with only a secondary right hand. However, in chapter 579 they were both depicted as also having secondary left hands whilst in their incomplete forms.
 * Members of the clan have been noted to access Susanoo without having their Mangekyō Sharingans activated.