Board Thread:Theories and Speculation/@comment-25547449-20150410054820/@comment-1512913-20150410112003

Black Zetsu didn't reconstruct her, that's a common misconception. She is the Ten-Tails, all Black Zetsu did was forcibly have Madara absorb too much chakra, which resulted in his loss of control over the Ten-Tails and that allowed Kaguya to take over.