Saiken

The is a tailed beast sealed within Utakata of Kirigakure. It has been captured by Nagato in the anime, then extracted and sealed by Akatsuki.

Утаката сдох одним словом

Appearance
The Six-Tails resembles a white, chubby, bipedal slug with small arms and feet. It has two prominent optical tentacles (eyes) and hole-like openings as a mouth. Its entire body is covered in a slimy substance.

Tsuchigumo Kinjutsu Arc
In the manga, the Six-Tails' capture is not seen. In the anime, before Taka began working with Akatsuki, Akatsuki was said to have seven tailed beasts. When Taka is sent to capture the Eight-Tails, the group has only six, the seventh missing beast being the Six-Tails. Utakata's capture is the subject of its own arc, though little is actually seen of the Six-Tails outside of Utakata's transformations. Utakata is captured by the Six Paths of Pain at the end of the arc and the Six-Tails is extracted from his body, resulting in his death.