Approximately one thousand years prior to the Invasion of Naboo, the Sith Lord Darth Bane enacted the Rule of Two. This teaching mandated that there would only be two Sith at any given time; a master to embody power, and an apprentice to crave it. As part of the Rule of Two, Bane took on an apprentice and passed his teachings onto his student. His apprentice escaped the notice of the Jedi. After the Jedi defeated Bane, his apprentice carried on the Rule of Two, which allowed the Sith to survive in secret while the Jedi falsely believed that the Sith had become extinct. Although the historical records weren't accurate about who the apprentice was, or how Bane died, it was considered possible that Bane was murdered by his apprentice.
Behind the scenesEdit
Darth Bane's apprentice was first mentioned in Terry Brooks' novelization for Star Wars: Episode I The Phantom Menace, based on backstory notes by Star Wars creator George Lucas. In Star Wars Legends, the character was identified as Darth Zannah.