Tailed Beast

The are nine giant demons in Naruto. Those seen thus far are slightly larger than Gamabunta, who is over 100 meters tall. The tailed beasts each have a different number of tails, and each is a different type of creature. Compared to humans, tailed beasts possess a massive amount of chakra, described in the series as the "ultimate chakra". Shukaku seems to possess a chakra level several times that of any human, while the nine-tailed fox's chakra is practically limitless. Despite their unrivaled strength and power, not all of the tailed beasts are able to use it as effectively. The three-tailed beast, for instance, did not possess the intellect to control its own strength, making it weaker.

Those within whom a tailed beast has been sealed at birth are called, and grow up to exhibit extraordinary powers. In some instances, they are actually stronger than the tailed beast they possess. This is because they have the knowledge to control the tailed beast's strength effectively, whereas an unsealed tailed beast may lack the necessary intelligence to do so. The host also tends to have some sort of physical characteristic akin to the tailed beast sealed within them (Naruto's whisker-marks, the rings around Gaara's eyes, and Yugito's slanted eyes). Naruto takes the word "host" offensively, regarding it as a dehumanizing term. According to Akatsuki members, those who host such creatures are typically lonely people who loathe humanity, and so far this has proven to be true (at least at first). When the first two were captured, no one from their villages cared that they were taken or lifted a finger to help; in fact, they were thankful to be rid of them. It is known that the death of a host will result in the death of the tailed beast within, and the hosts seen thus far sometimes exhibit involuntary defensive powers. Likewise, the removal of the tailed beast results in the death of its host.

During the Great Shinobi Wars, each country's Hidden Village tried to make use of the tailed beasts for military purposes, and competed for them. However, no one was ever able to truly bring the tailed beasts under control. The practice of sealing tailed beasts within humans to harness their powers proved the only effective method of harnessing the awesome powers of the beasts.

Akatsuki is currently collecting the nine tailed beasts. They capture the hosts and take them to a secret location where a three day long jutsu is performed to draw out the tailed beast from the host. They possess six tailed beasts: the Shukaku, the two-tailed demon cat, the three-tailed beast, and three other unknown beasts. Every one has been extracted and sealed.

One-Tailed Shukaku

 * Name: or
 * Creature type: Tanuki (raccoon-dog, native only to Japan and other Asian countries)
 * Host: None, formerly Gaara
 * Unique traits: Able to spit concentrated balls of wind mixed with chakra
 * Status: Captured, extracted, and sealed by Akatsuki

Shukaku is said to be the corrupted spirit of a Sand monk turned demon. He was originally sealed inside a teakettle and then placed inside his first host. He was sealed inside Gaara by Chiyo on the orders of Gaara's father, the Fourth Kazekage, using Gaara's mother as the sacrifice. Shukaku had two other hosts before Gaara, both of whom died when Shukaku was extracted from them. Shukaku is intelligent but also incoherent, giving him the demeanor of a drunkard. Shukaku itself can translate to "drunk" in Japanese. Like other tailed beasts, its innate rage and bloodlust influence its behavior, and it relishes in the opportunity to kill anyone in sight.

As a host of Shukaku, Gaara has the ability to move and levitate sand at will, and is protected at all times by the Shield of Sand, regardless of his will (even self-inflicted injuries are prevented by the sand). He also suffers from lifelong insomnia, a side effect of being Shukaku's host. Should he fall asleep, Shukaku would eat away his personality.

When angry or particularly bloodthirsty, Gaara begins to transform into a human-sized version of the Shukaku by layering sand over his body. The sand takes on the appearance of the Shukaku, and enhances his abilities greatly. While in this form, Gaara gains immense strength, endurance, and the ability to use Sand Shuriken. He can also stretch his sand limbs as he does with his regular sand, the primary difference being that his limbs remain just as strong as when they are retracted. This transformation seems to occur very slowly, as Gaara attempted to assume this form twice and was foiled both times. In the first instance, Sasuke injured him during an attempted transformation in the Chunin exam. The latter, which Gaara nearly completes, is ruined by Naruto during their battle in the forest. Gaara has only been able to reach a point at which all but his legs have been covered in sand.

In dire situations, Gaara can create a life-sized replica of Shukaku from sand. Unlike his human-sized version, this replica can be created almost instantly. Gaara controls the replica from within, remaining safe from enemy attacks. Despite being made of sand, Gaara seems to be unable to regenerate any damage caused to the replica. While in this form, Gaara can also release Shukaku's spirit, allowing the demon to use his full power. To do this, Gaara must emerge from within the replica, settling on the top of its head, and force sleep upon himself. Once released, Shukaku can attack with his signature ability, Wind Release: Drilling Air Bullet. Because Gaara protrudes from the top of Shukaku's head, he can be awoken, thus suppressing Shukaku's spirit once more.

During the Rescue Gaara arc, Shukaku was forcefully extracted from Gaara by Akatsuki, thus killing him. Fortunately for Gaara, he was resurrected through a combination of Chiyo's life-transferring technique and Naruto's chakra. Gaara's ability to control sand still appears to be intact, though to what degree remains unclear.

Trivia
 * Shukaku is sometimes mistaken for a badger, raccoon or a panda.
 * Tanuki, like kitsune, are magical creatures in Japanese folklore, and the two often appear as rivals.
 * There is a Japanese tale about a priest and a Tanuki sealed in a teakettle, called Bunbuku Chagama.

Two-Tailed Demon Cat

 * Name:
 * Creature type: Nekomata (magical, two-tailed cat)
 * Host: None, formerly Yugito Nii
 * Unique traits: Fire-breathing
 * Status: Captured, extracted, and sealed by Akatsuki

The two-tailed demon cat is a fire-breathing, flaming cat from the Land of Lightning. Its host was Yugito of Kumogakure, who was captured by the Akatsuki members Hidan and Kakuzu shortly after her introduction. Despite luring her two pursuers into a closed space, sealing the exits, and transforming herself into the demon cat, Yugito was overpowered and rendered unconscious (as well as pinned to a wall by a kunai through her hands) by the two Akatsuki members. Zetsu later arrives to take her off their hands. In chapter 331, Akatsuki begins extracting the beast from Yugito, and finishes in chapter 332.

Trivia
 * Although the two-tailed demon is depicted as a Nekomata, it doesn't seem to exhibit the same abilities as the legendary creature. The nekomata of folklore was said to animate and control the dead, while this nekomata has fire-based abilities. However, this is an indirect reference to a Japanese belief that spirits of the dead manifested as airborne flames, similar to will-o-wisps.

Three Tails

 * Name:
 * Creature type: unknown (Turtle-like creature)
 * Host: None
 * Unique traits: Unknown
 * Status: Captured and sealed by Akatsuki

The three-tailed beast is a gigantic, turtle-like demon that Deidara and his new partner, Tobi, captured. This creature may be based on the Genbu or the Kappa.

What abilities this creature possesses remains unclear, as it did little to actually attack the two in its short appearance. It is clearly quite fast despite its size, as evidenced by its ability to keep up with Tobi, who was running on the water at the time. With the Three-tails distracted, Deidara molded an explosive clay fish in an attempt to capture it. It's unclear if this marked the end of the battle, as the remainder of the battle goes unseen. Tobi gloated of bringing the Three-tails down with his special jutsu, but Deidara thought otherwise. In its last appearance, Deidara is towing the unconscious beast with two large clay birds.

Unlike the other tailed beasts seen thus far, the Three-tails lacked a host. It is different from the Shukaku and the Demon Fox as it isn't intelligent, which makes it little more than a wild animal. According to Deidara, lacking a host made the beast weaker because it wasn't intelligent enough to control its own strength.

The Akatsuki leader called in his subordinates to perform the sealing ritual in chapter 327, and they complete sealing the beast in chapter 331.

Nine-Tailed Demon Fox
See main article:Kyuubi

Legend of the Tailed Beasts
According to some fans, the "Legend of the Tailed Beasts" is an epic story from Japanese folklore which Naruto author Masashi Kishimoto draws from to create the tailed beasts in his work. It appears, however, to be an example of internet-based fakelore which originated on Chinese websites.

The veracity of the legend breaks when it is cross-referenced with non-fandom sources on Japanese folklore. For example, the isonade, which is held to be the three-tailed beast in this account, is in fact equipped with only one large, hook-covered tail, and the "houkou" (actually a Chinese creature called penghou), named as the five-tailed beast, has no tail at all.