Near a millenium ago before people could use chakra and constantly warred with one another, Kaguya came from a far away place seeking to eat Shinju's forbidden fruit to gain it's power for herself. She used her power to end the wars, and came to be worshiped as a goddess; the people called her the Rabbit Goddess. She would go on to bear two sons in her lifetime, Hagoromo and Hamura, who inherited her power. Her power had eventually corrupted her, making her conceited and arrogant and the people started to consider her a demon. She ultimately used her power to entrance the people, placing them into a coma-like dreamworld and connecting them to the Shinju. Shinju would ultimately take on a monstrous form to reclaim its stolen power, but her children defeated it and ended up sealing the god-like being inside of Hagoromo. Unbeknownst to them is that Kaguya was crazed and sought to take back the power her sons inherited from her, merging with the Shinju and twisting it. Before she was sealed along with Shinju, she created Black Zetsu, a physical manifestation of her will, to ensure her return. For around a millenia, Black Zetsu worked to bring its "mother" back and manipulated many people and events, and eventually it was successful. Now Kaguya is back, once again trying to place everyone on a coma-like dreamworld and take all the chakra for herself, includingNaruto's and Sasuke's who turn out to be her reincarnated grandchildren: Ashura and Indra
Now, we had our share of tiring filler episodes....but they finally made one, that answers my questions.
I actually want to know more about Hamura Otsutsuki; Technically the Hyuuga's second ancestor
Side note: I think Kaguya looks a lot more scarier in the manga