Saya

Saya is Jin Kisaragi and Ragna the Bloodedge's sister.

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.

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. 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 Clover work directly under her.

Since the day of her kidnapping, her appearance has changed vastly. She now has red eyes and long, purple hair. 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.

In The Wheel of Fortune Drama CD, which shows the timeline where Noel did not existed. 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 is 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.

The reason for Jin's hatred towards Saya, and why she suddenly became ill in the current timeline is currently unknown.

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 (Both English and Japanese) has the most characters that is voiced by her. (5 females: Saya, Noel, Nu, Mu, Lambda)