Darth Imperius and Sith ghosts

"The Dark Council". During chapter 2 of the Sith Inquisitor class story, they collect and bind a total of four Force ghosts of ancient Sith Lords. At the conclusion, the lightside Inquisitor, now known as Darth Imperius, is able to use the light side of the Force to redeem them, pacifying their restless spirits and allowing them to become one with the Force. (Video by YouTuber Darrell Story.)

Example of:
Quieting the Unquiet Dead