Serenity, a female entity, was one of the five enigmatic beings referred to as the Force Priestesses. She resided on a mysterious planet called the Wellspring of Life, situated at the center of the galaxy. Along with her four counterparts, she served as an embodiment of the connection between the Living Force and the timeless Cosmic Force. With a form that could change, she possessed the ability to retain her consciousness after her physical death. She behaved with composure, unlike her cousins, who represented the emotions of Anger, Joy, Sadness, and Confusion. Often acting as the spokesperson for her group, Serenity bestowed upon individuals the necessary instruction to attain immortality, a state the priestesses considered the "great gift," doing so in conjunction with the associated blessings of her cousins.
In 19 BBY, towards the conclusion of the Clone Wars, Serenity encountered Grand Master Yoda of the Jedi Order. To assess if he was deserving of their teachings, she and her cousins subjected the Jedi Master to a series of trials. After he successfully completed the challenges on their world, Serenity and the priestesses dispatched him to Moraband, the Sith's original home, for his final tests. Facing challenges of her design, the Jedi Master then confronted the Sith Lords Darth Sidious and Count Dooku. After he triumphed over the two Sith, Serenity judged Yoda worthy of the gift of immortality and declared that he would receive training from the deceased Jedi Master Qui-Gon Jinn.