Shukaku

, better known as the is a tailed beast that is sealed within Zyeta Uchiha of Konohagakure.

Background
According to Tobi, Shukaku first came into being in the waning days of the Sage of the Six Paths' life; to prevent the Ten-Tails' resurgence, the Sage split up its chakra] and used his ability to create nine separate, monstrous constructs of living chakra, which would become known as the Tailed Beasts. Citizens of Sunagakure believed that Shukaku was a of a corrupted Suna priest, and was originally sealed inside a tea kettle.

Personality
Shukaku is cunning, but also incoherent, giving it the demeanour of a drunkard, which fits well with the typical depictions of tanuki in Japanese folklore. According to Gaara, because of its innate rage and bloodlust, Shukaku relishes the opportunity to kill anyone in sight, even more so during a full moon. Like all tailed beasts, Shukaku also has a strong desire to preserve its own life, and as such, will grant its jinchūriki the power to control sand as well as allow them to transform into it in a state of need and bloodlust.

The Eight-Tails mentioned that Shukaku hates Kurama for its beliefs that the tailed beasts' strength is measured by the number of tails and, as such, views Shukaku as the weakest.

Appearance
Shukaku is a sand-coloured tanuki, with black (dark blue in the anime) markings all over its face, body, and tail, and a jagged, concave mouth. The sclera of its eyes are black, containing yellow irides with pupils that each takes the shape of a black four-pointed star with four black dots around it.

Abilities
Like all Tailed Beasts, Shukaku has an enormous supply of chakra. However, it does not have as much as Kurama. Shukaku has the power over wind, in which it uses to perform powerful attacks such as the Wind Release: Drilling Air Bullet; the ability to manipulate sand, using it as an effective weapon; and can perform the Tailed Beast Ball. At fully-released form, Shukaku's body is completely made of sand; as such he can ignore most damage that would otherwise be detrimental, as shown when he had one of his arms chopped off by Gamabunta and was still able to keep on fighting. Whenever Shukaku is sealed into its Jinchūriki, it has the ability to eat away its host's personality, and influence him or her with its bloodlust behaviour whenever he or she sleeps, which leads its host to develop insomnia.

Activity inside Gaara
As Shukaku's jinchūriki, Gaara has the ability to move and levitate sand at will. Shukaku was at first believed to be the source of the automatic Shield of Sand, however the Fourth Kazekage told Gaara that this was due to his mother's will being in the sand. When angry or in a state of bloodlust, Gaara can use the sand in his gourd to take on the form of a miniature Shukaku, or even create a giant copy of Shukaku's body.

Influence
is the Japanese name for the raccoon dog. The tanuki has been renowned for its mischievous nature and abilities to shape-shift and bring good fortune. Shukaku has ties to several tanuki archetypes. One is the Bunbuku Chagama tale, where a tanuki sealed inside a tea kettle is then placed inside its first host. In the series, Shukaku was reported to have been sealed within a tea kettle. Some tales state of a shrine priest being a tanuki in disguise, which ties into how, early in the series, Shukaku was reportedly a corrupted Suna priest.

Trivia

 * Since Gaara was infused with Shukaku prior to his birth, it would seem that its abilities were melded with Gaara's own; however, it's unclear if Gaara's control of sand and the wind element is a result of his own chakra or Shukaku's.
 * Shukaku is the only tailed beast to use an actual technique; the Tailed Beast Ball, which all tailed beast can use, is less of a technique by normal standards and more of a manipulation of pure chakra.
 * Previously, Shukaku was the only tailed beast with a given name. As of chapter 568, Son Gokū, the Four-Tails, revealed that all the beasts have given names from the Sage of the Six Paths.