Kaguya Otsutsuki is a new, but the current main antagonist of the Naruto manga and anime series. She is a princess who became the first human ever to hold and use the power of chakra, which her twin sons inherrited from her.
Kaguya Otsutsuki was a princess from an unknown land that at least a thousand years before the series began decided it would be in humanity's best interests if someone were to eat the forbidden fruit of the Shinju, a god-like tree, doing so to gain the power to put an end to war and create world peace. Though she was successful at doing so with the god-like powers she gained and used her Infinite Tsukuyomi to create world peace, it only last for a limited time, possibly because of her mortality, and the people of the world began to fear her as a demon for her methods, despite them having been genuinely out of desire for peace. Kaguya gave birth to two children, Hamura and Hagoromo, who inherited her power of chakra, and she went on to try and gather all chakra for so she could split it evenly among her sons by creating the Ten-Tails, which was formed from both her and the Shinju. However it, and by extension she, was sealed within Hagoromo by him and his brother and later sealed away in the moon along with the Ten-Tails body by him later in life. Neither of her two sons ever seemed to know it was her. Its also been implied they may have gone against her at some point too. After she was sealed in the moon, Kaguya's will produced an artificial being later known as Black Zetsu, which considered her its mother, and it went on to influence history as it wanted in order to revive Kaguya.
After Madara Uchiha had nearly succeeded in completely trapping the world in the Infinite Tsukuyomi, Kaguya Otsutsuki's will finally enticed Black Zetsu to betray the mighty Uchiha elder and revive her in his immortal body by having him absorb all the chakra from the genjutsu's victims and fully merge with him, thus transforming Madara into Kaguya herself. Effortlessly overpowering Naruto Uzumaki and Sasuke Uchiha, Kaguya recognizes them as the the ones her grandsons' chakras had been reborn into and, telling Kakashi Hatake that she didn't want further harm to come to the earth since its her precious nursery, Kaguya teleports herself and her opponents to a different dimension and lets them fall towards a stream of lava, declaring she would wipe them out. Though they all avoid the lava, she, declaring all chakra to be hers and that it would become as one again, disabled Sasuke's hawk summon and proceeded to attack and easily overwhelm Naruto, before being attacked from above by Sasuke using his perfect form of Susanoo. Easily overwhelming him and destroying his Susanoo instantly, Kaguya teleported through a space-time rift and held Naruto and Sasuke by their chins, paralyzing them, and began crying as she saw the images of her two sons in them. As the fight continued, Kaguya was struck by Naruto after witnessing one of his perverted techniques, but proceeded to teleport everyone again into a different, icy dimension, freezing Naruto and Sasuke in ice before they could seal her. Moving away through a space time rift, Kaguya reached through another, grabbed Sasuke, and tossed him into a desert dimension at Black Zetsu's request, so she could fight and defeat one at a time and ruin their chances of sealing her.Continuously overwhelming Naruto as the fight continues, Kaguya summons them all to a gravity-heavy deminsion after Obito uchiha and Sakura Haruno manage to retrieve Sasuke, which ways down everyone, including her, Kaguya attempts to kill Naruto and Sasuke with her destructive bones, which miss. Adjusting, but allowing Kakashi Hatake and Obito to move again, Kaguya attempts to kill them again, only for Obito to take the hit and save the others. After Obito crumbles away, Kaguya has her left arm knocked off by Naruto, before proceeding to be overpowered by him and then once again overwhelming and destroyed Sasuke's perfect form of Susano'o. However, the Tailed Beasts within her then force a transformation on kaguya against her will, which emerges from the hole where her left arm was. Though she managed to subdue it, Kaguya went on to be sealed by the combined efforts of Team Seven, thus ended her threat and removing her essence and the Tailed Beasts from Madara's body
Kaguya was a very frightening person, but despite it she was a well-meaning woman who desired to create world peace, just as her son Hagoromo did. Unlike him, however, Kaguya opted for a more forceful approach, creating the Inifinite Tsukuyomi genjutsu and using it on the world to force them to submit to her will by putting their minds in a dream world so that war wasn't possible. This method only caused others to fear her as a demon, and though she still wanted to create world peace permanently after her revvial, it seemed she them also wanted to rule the world since she tried to create an army from the Infinite Tsukuyomi's current victims. Shes was also ruthless, as she tried to sacrifice one of her own descendants to be able to permanently achieve her goals, and moved to destroy Team Seven without any hesitance after her revival, seeing them as a threat to her plans, despite the fact that Naruto Uzumaki and Sasuke Uchiha were following her son, Hagoromo's wishes. Uniquely, she seemed to love the earth and its natural state, and didn't want any further harm to come to it after her revival. Despite their different views, yet similar desire for world peace, its been implied that Kaguya's fraternal twin sons, Hagoromo and Hamura, might have gone against her at some point and that, put together with them leaving her after growing up and ultimately sealing her in the moon(though they were unaware of her at this point) has caused Kaguya to develope negative feelings for them. However, she still showed motherly qualities as Black Zetsu, a product of her will, has stated that Kaguya wanted to gather all chakra to herself in order so that she could split it among her children and benefit them in a way, therefore making it likely that what they did to her feels like an ultimate betrayal. Kaguya also began crying when she saw the images of Hagoromo and Hamura in Naruto and Sasuke, which suggested she, as their mother, still loved them.