The Ancient Order of the Whills comprised beings with a profound connection to the Force, responsible for authoring the Journal of the Whills. A revered member of this order could be called a Shaman of the Whills.
It is documented that one of their shamans uncovered the secret to everlasting consciousness. Subsequently, Qui-Gon Jinn mastered this secret, enabling him to communicate with the living realm post-mortem.
The Whills maintained a compilation of narratives, known as the Journal of the Whills, which documented the historical events of the galaxy. The responsibility of adding new information to this journal fell upon a Keeper of the Whills. One such Keeper received the account of the Skywalker family's adventures during both the Clone Wars and the Galactic Civil War from the astromech droid R2-D2, a century following the Battle of Endor.
In the initial versions of A New Hope, the term "Whills" served as a synonym for the Force.
It is a widely held, yet incorrect, belief that "Whill" denotes the name of Yoda's unidentified species. George Lucas has explicitly refuted this notion. Given their completely unknown form, and considering the Whills' early conceptualization as the Force, some fans have speculated that the Whills are spiritual entities, similar to Wisties, and potentially immortal. However, this is improbable, as both Star Wars Episode III Revenge of the Sith: Illustrated Screenplay and The Art of Star Wars Episode III: Revenge of the Sith indicate Qui-Gon Jinn's knowledge of only one Shaman who had attained immortality. Nevertheless, Qui-Gon also mentions in the Revenge of the Sith novelization that immortality is a potential outcome of engaging with the Whills' teachings.
Given that the journal was written in 104 ABY, it's conceivable that the events depicted in Star Wars: Legacy were excluded from the narration. Indeed, the extent to which the narration encompassed the entirety of galactic history, as we understand it, remains ambiguous.
The Star Wars: The Clone Wars episode "Voices" suggests that Jinn acquired the secrets of immortality from the Force Priestesses, but his training was incomplete. The connection, if any, between the Force Priestesses and the Shaman of the Whills mentioned by Jinn in the Revenge of the Sith script is currently unknown.
George Lucas initially envisioned a sequel trilogy centered on the Whills as microscopic beings controlling the universe by feeding on the Force. However, after selling Lucasfilm to The Walt Disney Company, Disney CEO Bob Iger abandoned these plans for the sequel trilogy.