Qui-Gon also appeared as a Force ghost in one of the short stories of From a Certain Point of View, "Master and Apprentice," and his voice, along with the voices of other Jedi, was heard in both "There Is Always Another," and during the climax of The Rise of Skywalker on Exegol.
George Lucas similarly could have added Qui-Gon Jinn to the Force ghost mix if he deemed him an appropriate inclusion. However, Qui-Gon Jinn played no part in the original trilogy whatsoever, so having him appear would have been entirely out of place for the story.
Qui-Gon Jinn appears to Kenobi for the first time as a Force spirit. The first known Jedi to learn the secret was Qui-Gon Jinn, who learned it from a Shaman of the Whills. His training remained incomplete at the time of his death, so he could only manifest as a disembodied voice.
Force Ghosts have become part of the Star Wars franchise's lore, expanded upon in movies, numerous canon tie-ins, and even the Obi-Wan Kenobi Disney+ TV show. Some of the greatest Jedi returned as Force Ghosts: Qui-Gon Jinn, Yoda, Anakin Skywalker, Luke Skywalker, and Leia Organa.
Summary. The ending of The Rise of Skywalker sees Leia as a Force ghost, but it's never explained how she was trained to do this after her death. Leia's ability to become a Force ghost isn't far-fetched, as she had three Jedi Masters who could have taught her - Luke, Obi-Wan, and Yoda.
Mace Windu appears as a Force ghost in the alternate history comic Star Wars Infinities: The Empire Strikes Back in a vision to Darth Vader, though this may only be a mental vision in Vader's mind as opposed to an actual Force ghost.
Originally Answered: Why doesn't Ben Solo appear as Force Ghost? Because he's now literally a part of Rey. Earlier in the movie, Rey healed that snake thing and said she transferred part of her life force to it. That was foreshadowing that when Rey died it look all of Ben's life force to grind her back.
...was redeemed at the end like Vader was. We will see a force ghost of Maul who will be trained by Qui-Gon to be able to live forever in the Force. He accepted his defeat and the Dark Side died inside of him in his last moments as Kenobi held him.
The closest that Star Wars canon has come to naming who trained Yoda was revealing that Jedi Master Qui-Gon Ginn was the one who taught Yoda to become a Force Ghost and attain immortality.
In material that is now considered Legends, Qui-Gon is even described as a Gray Jedi. Additionally, the term has also been applied to Force-sensitives who aren't affiliated with the Light or Dark side of the Force. Quite literally, these Gray Jedi don't see things in black and white, or light versus dark.
His connection to the Light Side was too strong, and indeed, his willingness to follow it over the dictates of the Council made him far more dangerous to Darth Sidious' plans.
Legend had it that Yoda—a Jedi who became Grand Master—was trained by N'Kata Del Gormo. A Force-sensitive Hysalrian, N'Kata Del Gormo was trained in the ways of the Force and achieved the rank of Master within the Jedi Order.
Because Maul punched him with the hilt of his saber and then stabs him faster than Qui-Gon can pull back his blade. So Qui-Gon lost because Maul was physically stronger and quicker than him. Qui-Gon is skilled but not a prodigy. And he's quickly worn down by Maul in both their encounters.
CANON: Only the Jedi can become Force ghosts, and at least 12 Jedi have done so. They can speak to someone who is strong in the Force, but can only be seen by someone who knew them. They may be immortal.
Qui-Gon: I cannot. My training was incomplete. As such, he can only ever materialize as a disembodied voice in the physical world. The other Jedi who have achieved oneness with the Force have disappeared upon death, such as Yoda, Obi-Wan, and Luke.
When Qui-Gon passed the Jedi Trials and became a Jedi Knight, Dooku told him not to trust others because his need to reach out to others left him vulnerable to betrayal. When Qui-Gon was killed by Darth Maul, Dooku was so saddened that Qui-Gon's death lead to Dooku's transformation into the Sith Lord Darth Tyranus.
However, Grogu was captured by Imperial forces, and Djarin was forced to lead a mission to rescue him. After being reunited with Grogu, Djarin delivered him to Luke Skywalker, a Jedi who agreed to take the child into his care and train him in the ways of the Force.
These characters include Ahsoka Tano, Kanan Jarrus, Luminara Unduli, Aayla Secura, Mace Windu, and Adi Gallia. While those mentioned have never appeared physically as a Force ghost, their Force connection with Rey can surely be classed as a Force ghost appearance in Star Wars canon.
Regardless, based on the season 7 of The Clone Wars, and the fact that Darth Maul was aware of Anakin Skywalker's future and his role as the Chosen One, it is very likely that Darth Maul indeed feared Darth Vader to some extent, and preferred to avoid a direct confrontation with him, at least, on his own.
Anakin's spirit did return to help Ahsoka overcome her past trauma and to make amends with his former Padawan for the terrible things he did as Darth Vader. The last shot of Ahsoka season 1 presents the scene from his perspective, removing all doubt that he was only in Ahsoka's head.
Though initially trained as a Jedi by his uncle Luke Skywalker, Ben was seduced to the dark side of the Force by Supreme Leader Snoke, and aspires to be as powerful as his grandfather, the Sith Lord Darth Vader / Anakin Skywalker.
during the battle, Ben lets Ghostfreak possess him so that his DNA is re-transferred to the Codon Stream. Ben then changes into Ghostfreak to control Ghostfreak but Ghostfreak possesses him and knocks out his friends. He then challenges Vilgax who weakens him with the light from his sword.
It seems that with his last ounce of strength, Ben gave what was remaining of his life energy to save Rey. This was his last sacrifice, effectively acting as redemption to return him to the light side of the Force. That is why his body vanished, as Jedi like Luke Skywalker and Obi-Wan Kenobi and Leia did before him.
