Saya

Saya is the current Imperator of the Novus Orbis Librarium, as well as the younger sister of Jin Kisaragi and Ragna the Bloodedge.

Information
Saya was born with a frail body, and throughout her life was bullied by her brother Jin. Her other brother, Ragna, was much more caring, and spent much time with her. Jin grew jealous of the relationship Ragna and Saya shared, and eventually attempted to kill her, immediately after she gave Jin the Yukianessa. She was kidnapped by Terumi Yuuki the same night, and given unconcius to Relius Clover. Acording to the Drama CD The Wheel Of Fortune, Relius and Terumi were planing to use her body as a "Vessel" for something, however, what was sealed inside her, it is unknown to date.

Noel Vermillion, Lambda-11 and ν-13, as well as the unseen prime field devices 1-10 are all copies of her, sharing her physical traits, but none of her memories, However, the reason of why is she the basis has yet to be explained. During BlazBlue: Continuum Shift, it is revealed that Saya had been alive throughout the years, and was currently the Imperator of the NOL, while Hazama and Relius work directly under her.

Since the day of her kidnapping, her appearance has changed vastly. She now has red eyes and long, purple hair; it is also interesting to note that she doesn't seem to have aged at all; also her personality its totally different- not acting like herself, speaking in an archaic tone. As Imperator, she rules the world and goes by the name "Imperator Librarius".

While Ragna sacrifices his left arm to turn Mu (μ-12) back into Noel, Saya destroys the Master Unit, Amaterasu, while nobody's looking, and takes control of Takamagahara, thus granting herself the one wish she had always wanted: to prevent time from looping any longer and make the world the way she believes it should be; a "World of Death" where death is permanent, and when things end once, they shall end permanently. The reunion with her brothers was vague, as she didn't direct a word at either of them.

In The Wheel of Fortune Drama CD, which shows the timeline where Noel did not exist. It was revealed that when they were young, Jin and Saya are very affectionate towards each other. They were happily playing together, and Jin's attitude towards Saya was completely different from the current timeline. With Saya giving Jin a crown of flowers she had made, and saying that she loves Jin very much. This is seen through a vision by Tsubaki, and she immediately displayed jealousy towards Saya; screaming at her to get away from Jin.

Trivia

 * Saya can be said to be the BlazBlue counterpart of Guilty Gear's That Man. Both are very mysterious characters that age abnormally (Saya does not seem to have aged much, if at all, since the day she was kidnapped whereas That Man ages backwards). Both wield immense power that far surpasses that of the main protagonist, and they have numerous servants which includes some of the playable characters.
 * Concerning their two main servants; Both have one that is calm and collected (Relius/Raven) and another who is wild and destructive (Terumi/I-no).
 * Saya's voice actor (for when she is a child) in both the Japanese and English dub has the most characters that is voiced by her, those being Noel, Mu, Nu, Lambda, and Saya herself.
 * In The Wheel of Fortune Drama CD, Terumi brought and unconscious Saya to Relius just after he burned down the church, while Relius commented that her body will be useful for a "vessel", impliying that her role at the end Continuum Shift's true ending may be linked to being possessed, and not her actual conscious.