Shukaku

Shukaku is one of the 9 legendary tailed beasts, or bijuu. He acts drunken and crazy most of the time, and shows little regard for the well-bieng of anything else. He had several hosts before the fourth Kazekage implanted the demon inside his own son, Gaara. Because of the implant, Gaara gained many of the beast's powers, most notably sand manipulation. Whenever Gaara fell alseep, however, Shukaku took over his body. Gaara taught himself to not sleep at all to prevent the tailed beast to come out. Eventually, during the Chunin Exams, he was allowed to be unleashed from inside Gaara when Gaara fell asleep. He fought against Naruto Uzumaki and Gamabunta. Together they beat the beast, who retreated back inside Gaara for safety. After a few years, the Akatsuki captured Gaara and extracted Shukaku from him.