Masago

Masago was a female human Sith Lord and a royal family member. For some time, she kept her Sith nature in hiding, until finally revealing it by killing her brother, the king, when an opportune moment presented itself. After overthrowing the king, Masago took power for herself. Some of her political measures included banishing Princess Misa from the palace, and setting up checkpoints to protect it.

Upon hearing about the king's death, Misa and Jedi Knight Tsubaki, who once worked for the king, teamed up to try to take down Masago. The Sith Lord fought Tsubaki at the palace, and tempted him to join her in the dark side of the Force. During the fight, Tsubaki accidentally struck down Misa, and, in order to save her life, he accepted Masago's offer to become her Sith apprentice and they use the Force healing to heal Misa.

Text and facts from the “Masago” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.