And, a warning for people with weak hearts, please look away now:
Shukaku is one of the "bijuu", a tailed beast of the ancient world. Seeking a way to create a ninja with a large amount of chakra that would be an unstoppable machine, the Kazekage imbued Shukaku within his unborn son. Skikaku allows the user to have a unique control over sand, even small particles of it in rocks.
