"The ability to defy oblivion can be achieved, but only for oneself. It was accomplished by a Shaman of the Whills. It is a state acquired through compassion, not greed."
One of their Shamans was known to have discovered the secret of eternal consciousness and later, Qui-Gon Jinn learned the secret, allowing him to interact with the living after his death.[1][2]
In early drafts of A New Hope, the name 'Whills' is equivalent to the Force.
"Originally, I was trying to have the story be told by somebody else (an immortal being known as a Whill); there was somebody watching this whole story and recording it, somebody probably wiser than the mortal players in the actual events. I eventually dropped this idea, and the concepts behind the Whills turned into the Force. But the Whills became part of this massive amount of notes, quotes, background information that I used for the scripts; the stories were actually taken from the Journal of the Whills."
It is a common misconception that "Whill" is the name of the unknown species of Yoda. George Lucas has firmly denied this. Because their form is totally unknown, and since the Whills were an early concept of the Force, some fans have speculated that the Whills are of spiritual substance more or less like Wisties and probably immortal. However, this is unlikely to be true, as Star Wars Episode III Revenge of the Sith: Illustrated Screenplay and The Art of Star Wars Episode III: Revenge of the Sith both have Qui-Gon Jinn stating that he knew of only one Shaman who had achieved immortality. However, Qui-Gon also states in the Revenge of the Sith novelization that immortality is a possible end-result for working with the Whills' teachings.
Since the journal was composed in 104 ABY, it's possible that the events explored in the Star Wars: Legacy were not part of the narration. In fact, it is unclear to what extent the narration covered the history of the galaxy as we know it.