Character Profile: Shukaku

The One-Tailed Shukaku is a giant sand tanuki (racoon dog) who cares for nothing more than to satisfy his bloodlust. Said to have been the rage-full spirit of a priest sealed in a kettle, Shukaku was sealed into the body of Gaara, his father hoping to use Shukaku's power for the Villiage Hidden in Sand. Though Shukaku provides Gaara protection and power over sand, the monster drove Gaara into becoming a sleep-deprived sadist, as if Gaara sleeps, the Shukaku takes total control of his body while shattering Gaara's mind even further.

Naruto and Gamabunta are forced to fight the fiend during the Invasion of Konaha using the sand-based replica Gaara created in the Bijuu's image as a vessel before Naruto manages to wake Gaara up to stop Shukaku and convince his host to stop killing.

Eventually, the Akatsuki came to the Village Hidden in the Sand to abduct Gaara, and succeed in removing Shukaku from Gaara's body, sealing the Bijuu into a statue.

Shukaku is a giant sand tanuki (which is a dog-raccoon type creature common in Japan) who has been sealed into a boy when the boy was born. This boy is Gaara of the Sand. His other container was a high priest. If you contain Shukaku, you cannot sleep or it will take over.

Some of the time it will awaken and take over on its own. It usually starts to awaken when there's blood near you. It is one of the nine bijuu "# of tails demons", just like Kyuubi.