Board Thread:Theories and Speculation/@comment-1872728-20181213131712/@comment-30323490-20181213134537

They didn't transform into Hagoromo or Kaguya.By Sage Transformation they acquired Six Paths Senjutsu, which is something that Hagoromo (and Hamura) had before becoming the TTJ. Also the ten-tails at his fullest is Kaguya combined with the shinju. When Madara (and Obito) sealed the ten-tails into themselves they sealed just the Gedo Mazo + (almost) all 9 bijuu. Kaguya this whole time was still sealed away. Alive, but sealed away.