Jocasta started out as a Jedi researcher searching for information to be added to the Jedi Archives. She took Jerec as her padawan and became a Jedi Master, After becoming a the Jedi Archives librarian, Jocasta was delegated as a member of the Jedi Council. She served the Council for ten years and came to know many Jedi Knights including Dooku.
After stepping down from the Council, Jocasta Nu became the main librarian of the Archives and protecting it from intruders. Ahsoka Tano was assigned by the Council to help Jocasta guard the Archives after disobeying orders from Anakin Skywalker. Cad Bane was hired by Darth Sidious to break into the Jedi Archives to pick up a Jedi Holocron. Bane gathered a Clawdite to help him by shape-shifting into Jedi Knight to slip past the Archives' defenses. The Clawdite knocked out Jocasta Nu and assumed her shape. Ahsoka noticed the trickery and defeated the Clawdite.Jocasta Nu was at the Jedi Temple when Darth Vader lead the 501st Legion to kill the Jedi. Nu told her padawan Rayce to flee the temple through its secret passages while she holds off the Legion. Darth Vader ordered Nu to access the signal beacon. Nu denied Vader of the beacon and fought him only to be slained by the new Dark Lord.