Board Thread:Naruto Discussions/@comment-28414362-20150812151040/@comment-2140588-20150812154939

"Hagoromo and Hamura Ōtsutsuki used it(Rikudo Chibaku Tensei) to create the moon and trap the Ten-Tails' body(Demonic Statue of the Outer Path) inside of it." Pretty sure this sentence comes from the Fourth Databook. So.. the story was probably retconned.