Force Priestesses

The Force Priestesses were five beings that resided on the Force planet/Canon, the home of the midi-chlorians.

Biography
The priestesses were representative of the connection between the Living Force/Canon as experienced by living beings, and the Cosmic Force/Canon in its role in the greater scheme of the universe. The five were a form of shape-shifter, and would mutate their forms to manifest as Serenity, Joy, Anger, Confusion, and Sadness.

Jedi Master Yoda encountered the Force Priestesses during the Clone Wars. They knew the secret to transforming into a force spirit.

Behind the scenes
Though installments from The Lost Missions of Star Wars: The Clone Wars indicated that Qui-Gon Jinn had learned from the Force Priestesses and directing Kenobi to them as well, canon material from the the official Databank and the now-defunct Encyclopedia on StarWars.com still refer to Jinn as having learned from a "Shaman of the Whills," the Ancient Order of the Whills having first been referenced in the novelization of the original Star Wars film.