Isobu

Three shrimp-shaped tails trail behind Isobu, whose bulk reads as an enormous turtle fitted with a crab-like carapace and spikes bristling across its frame. Reddish muscle shows beneath the shell, and it moves on a pair of human arms with no back legs at all. Its face sits wedged between a jutting brow and a heavy jaw, each studded with points, while its red eyes hold crimson pupils, colored yellow in the anime. The right eye stays shut; Guren guesses the beast shields its one soft, unarmored spot. Back in the Sage's era it looked much the same, only smaller and with stubbier spines.

Soft-spoken and gentle, Isobu refers to itself with boku, a humble pronoun favored by young boys. Because Yagura tamed it and formed a true friendship with it, the beast is understood to be milder than several of its brasher siblings, coexisting peacefully with the host who carried it.

Hagoromo Otsutsuki brought Isobu into being by splitting the Ten-Tails' chakra among nine new bodies, and the beast eventually passed through several jinchuriki: sold to Kirigakure as a gesture of goodwill, forced into Rin Nohara as part of a foiled plot to loose it inside Konoha, then bound inside Yagura, the Fourth Mizukage, the only host to reach full harmony with it. Like every tailed beast it cannot truly die, reforming in a younger body each time it falls, which makes it the first of the nine known to have perished and returned.

Its layered shell and spines turn aside nearly any strike, and it can curl into a spinning sphere to barrel across the field, lash out with its three barbed tails, grow coral, and swim at blistering speed. Beyond raw defense it commands immense chakra it can share with others, rapid healing for itself and allies, and an affinity for Water Release strong enough to shatter a cliff. The anime adds a hallucinogenic mist that preys on a victim's fears, tidal waves and shockwaves, a swarm of miniature copies that devour whatever it swallows, a pocket dimension it slips into to hide, and the signature Tailed Beast Ball. Its lone weakness is the eye it keeps closed, the single part of its body it cannot armor.