The Nightsisters: Unlocking the past is a collection that is started and completed in the Elite Artisan profession specific quests given by Sage N'um in the Nightsister version of the Witches of Dathomir Theme Park.
The collection is started and completed with the completion of the Repair the Altar of Power quest.
Completion of the collection rewards the player with the Nightsister Unlocking the Past Badge.