Notably, the ghost of Aidan Bok could make itself solid enough to shove Tash Arranda through a doorway. A manifested spirit could wield Force powers, although not all of them.It also might have the ability to travel instantaneously to any point in the galaxy by force of will.
A Jedi must receive special training to become a Force Ghost
Those who died and passed into this netherworld of the Force generally could not affect the material world. However, some individuals can train during their lives to become Force Ghosts, retaining the ability to influence the galaxy after death.
Without question, the most powerful Force ability present in Star Wars is the Thought Bomb. It is created through an ancient Sith ritual where the Sith combine their dark side powers. If done successfully, the Thought Bomb can destroy all Force-sensitive beings unfortunate enough to be within the radius of its blast.
For years he served as Palpatine's right hand man, but he was ultimately redeemed by the faith of his son, Luke Skywalker. Now a Force Ghost, Anakin continues to act as an agent of balance.
This implies that Force ghosts are not actually immortal, in Legends at least. While Obi-Wan's Force ghost faded away after 9 years, Luke's Force ghost appears to Cade Skywalker much longer after his death.
Film Theory: Star Wars, Why don't Force Ghosts do EVERYTHING?
Why are Force ghosts so powerful?
Force spirits, also known as Force ghosts, were beings who gained immortality through the preservation of their consciousness after death. When lifeforms died, they became one with the Force.
In theory, Force spirits could neither harm or be harmed by physical entities, due to their spiritual nature. For the same reason, they could pass through solid matter effortlessly and were never hampered in their movements.
Star Wars has officially confirmed Sith spirits are in no way comparable to Force Ghosts. The idea of Force Ghosts runs all the way back to the first Star Wars film released in 1977, in which Obi-Wan Kenobi allowed himself to be cut down by Darth Vader.
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.
Galen Marek, better known as Starkiller, was the main protagonist of the Legends games before Disney bought Lucasfilm. He displayed incredible control of the Force, from moving a Star Destroyer to defeating both Vader and Palpatine in succession.
Force lightning ability was not restricted to dark-siders. Jedi and other light-siders who were strong of will and character could learn this power without falling to the dark side—but its use was viewed as inherently corrupting, and most Jedi Councils forbade its use.
Becoming a Force Ghost was a lost art that Qui-Gon rediscovered. Qui-Gon never completed the process, which is why he only ever appears as voice instead of a full ghost, but he taught it to Yoda and Yoda taught it to Obi-wan.
Leia (who was not explicitly Force sensitive at this point) doesn't acknowledge the Force ghosts at all, heavily suggesting that she can't see them. Moreover, the trio of ghosts aren't exactly well hidden - surely one of the revelers would've noticed them if such a thing were possible.
However, Palpatine was never able to achieve the immortality that the Jedi possess. His plans brought him closer than any other Sith to becoming a Force Ghost. But his failure proves that so long as the darkness outweighs the light, the Dark Side will never lead to immortality.
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.
Why didn't Mace Windu showup as a force ghost? Qui Gon died before he could finish his training so he can only appear as a voice and not a physical form. Mace Windu never studied or trained in that aspect of the force.
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.
In the Revenge of the Sith Visual Dictionary, under Darth Vader, in the Data File, it says -"As a result of having artificial arms, Darth Vader will never be able to conjure Sith lightning-nor be invulnerable to it."- Thats probably why Vader suffered so much in Return of the Jedi.
According to Imperial Estimates in Star Wars Inside #87, only about 100 of the Jedi survived Order 66. Most were subsequently hunted down and killed in the years following the Great Jedi Purge.
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.
