Susanoo (HBH)

Susanoo is a gigantic, humanoid being made of the user's chakra that surrounds them and fights on their behalf. It is the strongest ability available to those who have awakened the Mangekyō Sharingan in both eyes.

Attributes
When activated, Susanoo forms around the user and becomes an extension of their will, acting and attacking on their behalf. By default, Susanoo is anchored to its user and they to it: in its less developed forms it will move around with the user; in its more completed forms the user will be suspended within Susanoo, being brought with it as it moves around. This connection allows Susanoo to shield against physical attacks, one that becomes more difficult to penetrate as it is manifested more fully. If it is damaged, Susanoo does not regenerate and it can only be repaired either by advancing it to the next developmental stage or by dispersing it and then forming it anew.

Although Susanoo is quite effective as a defence, it is able to distinguish in what it blocks. For example, the user can still perform jutsu while within Susanoo and the attacks will pass through it without complications. Others can be brought within Susanoo with the user's permission, and users can likewise choose to leave Susanoo's protective envelope. The latter property can be used against the user, as if an opponent can bypass Susanoo, however slightly and latch onto them, they can be pulled out of Susanoo. With continued mastery, Susanoo can have increased defensive capabilities even at its ribcage stage, as seen when A was able to crack a rib of Sasuke's Susanoo, but could not even crack Madara's. Susanoo is also only able to defend against physical attacks, so they are still vulnerable to visual

So long as it is active, Susanoo draws on the user's chakra in large amounts. Sasuke Uchiha describes the sensation of using Susanoo as feeling pain in every cell in his body, which only increases over time and at higher developmental stages. Being a Mangekyō Sharingan-based ability, it also places a strain on the user's eyes the more it is used. However, it is not actually necessary for one's Mangekyō Sharingan to be active while using Susanoo.

Development
Susanoo has several developmental stages. Practised users go through all the stages every time they manifest it, layering more advanced stages over earlier ones or stripping them away as is needed; they can choose to stop at any developmental stage along the way if they choose to. At its simplest level, users only manifest aspects of Susanoo's skeletal structure, such as a ribcage for basic defence or an arm for interacting with the surroundings. Once a full skeleton is made, musculature and, later, skin forms until finally a complete humanoid is shaped. In these early stages, typically only the upper half of Susanoo is materialised, with legs becoming common once it reaches its full humanoid form; however, not all Susanoo users can accomplish the latter feat.

In its next stage, armour forms around the humanoid for further protection, causing it to resemble a yamabushi. In its final stage, users stabilise the chakra that comprises Susanoo to create a colossal form known as the, the ultimate ability of the Mangekyō Sharingan. In this state, Susanoo gains a tengu-like nose, wings for flight, and is clad with robes and ornate armour. This form possesses power comparable to that of a tailed beast, capable of levelling giant mountains and, when enhanced by Six Paths Chakra, small planetoids with ease. Users can also channel their own techniques into the Complete Body — Susanoo, as well as shape it around the Nine-Tails to improve its offensive and defensive capabilities.

Users are able to mingle the chakra that makes Susanoo with chakra from other sources. While in his Ten-Tails jinchūriki state, Menma was able to utilize the chakra of all combined tailed beasts, drastically improving its strength and causing lightning to emanate from its back.

Trivia

 * Although considered to be a Mangekyō Sharingan ability, Menma Uzumaki was able to awaken Susanoo only with his Rinnegan.