Naruto Community

Names: Six Tails
Host: None, formally Utakata.
Unique traits: Unkown.
Status: Captured and sealed by Akatsuki.

According to Madara Uchiha, the Six-Tails first came into being in the waning days of the Sage of the Six Paths' life; to prevent the Ten-Tailed Beast's resurgence, the Sage split up its chakra and used Izanagi to create nine separate, monstrous constructs of living chakra, which would become known as the tailed beasts. The Six-Tails eventually fell into the possession of Kirigakure and was sealed into Utakata.

According to the anime, at some point before his appearance, Utakata's master, Harusame, tried and failed to remove the Six-Tails from within Utakata to save his student from being a living weapon for his village. Utakata, however, having not heard what his master had said to him, later came under the assumption after the incident that his master had tried to kill him. This failed removal resulted in Utakata transforming into the Six-Tails and killing Harusame.  The Six-Tails resembles a white, chubby, bipedal slug with small arms and feet. Its entire body is covered in a slimy substance.