Madame Jocasta Nu was a Jedi Master and former member of the Jedi High Council who left the Council in the decades prior to the outbreak of the Clone Wars. During the war Nu was based on Coruscant where she worked as the Chief Librarian overseeing the Jedi Archives. As part of this responsibility, Nu could normally be found tending to the Archives and helping knowledge seekers sort through the vast repositories of knowledge.
As part of Cad Bane's plot to steal a vital information crystal detailing the names and whereabouts of every known Force-sensitive child in the galaxy, Cato Parasitti, a Clawdite bounty hunter, imprisoned Nu. This plot would be uncovered by Jedi Padawan Ahsoka Tano who had been assigned to assist Master Nu in the Archives as punishment for her disobedience on Felucia.