Saiken

Saiken takes the form of a huge, upright slug whose white hide carries a faint bluish cast and glistens beneath a coat of thick slime. Stubby limbs, six lengthy tails, and a pair of prominent eye-stalks give it its shape, while simple holes serve as its mouth. Back in the earliest days of the Sage of Six Paths it was far smaller than it would later become, yet even then it dwarfed its own maker.

Little of Saiken's temperament was ever revealed, but the giant slug refers to itself with the boastful pronoun "ore" and speaks in what may be an Osaka-flavoured dialect, delivered in a high, lively voice in the anime. It proved gentler than most of its kind, readily lending Utakata its power to rescue a friend and later withdrawing into him without any attempt to seize control. Even so, it would kill to survive, as it did when Harusame tried to tear it from its host. Sealed within Utakata for years, Saiken was eventually extracted by Nagato's Six Paths of Pain, an act that claimed its jinchuriki's life.

As a tailed beast, Saiken commands an enormous reserve of chakra that it can freely pass to others, along with potent healing that knits wounds in itself and its allies within seconds. It is effectively deathless, reviving in a younger body whenever it is slain. Among its deadliest weapons are corrosive discharges, released as liquid or gas, that dissolve a target the instant they make contact. Tremendously durable and attuned to Water Release, it can spew a clinging, adhesive fluid to bind its foes and, like every member of its kind, form a Tailed Beast Ball. During the Fourth Shinobi World War it was turned against Kakashi and Guy while under enemy control, joined Naruto within the shared consciousness of the beasts, and was freed at last to help bring the conflict to a close alongside its siblings.