Board Thread:Rebirth: Applications/@comment-4080775-20141013182134/@comment-4080775-20141018151958

Well, I scraped the Pocket Dimension Idea.

Kumogakure shinobi used to Heaven's Chakra Seal to seal up Matatabi as well as begin draining its chakra from it (weakening it in the process) and storing the chakra within the user that initiated the seal. They then used the Dimensional Spectrum Seal to transfer it to a new, more secure location, instead of it being visible outside.

The Heaven's Chakra Seal would keep the tailed beast contained, as well as keep it's chakra level in check.