Blue Ghost Force Ghost

In the Star Wars universe a Blue Ghost also known as Force ghost, means the Jedis who have died. It is the belief of many commentators which is influenced by the Star Wars movies that the Jedis who die unite with the Force and their bodies disappear, giving them the ability to come back if they so desire in the form of apparitions to guide others.

While many others are also of the view as inspired by the Star- Wars spin-off material that it applied even to the fallen Jedis or Sith like Darth Vader and Ulic Qel-Droma.They were repentful when their life came to an end because the rigors of their craft would rival that of pure jedi. However in the Revenge of the Sith it has been clarified that the come back as the Blue Ghost or the force spirit is not possible for every Jedi as it involves a very difficult discipline.

Qui-Gon Jinn is said to have mastered the way to immortality and discover the actual procedure of retaining his identity even after the inevitable death and the take over of Force by the method of achieving the state of unconditional compassion. Many also held this belief that his Blue Ghost has led Yoda and Obi-Wan to know about this discipline and follow it during the span of their exiles.

Darth Vader was unknown of this procedure and was shocked when he found the body of Obi-Wan getting disappeared when he killed him on the Death-Star in Episode IV.George Lucas had already shown on the Episode III DVD commentary that the coming back of Vader's former self, Anakin Skywalker, as the Blue Ghost at the end of the Episode VI is because of the mixed efforts of Anakin's latent Force ability which he possess and the attainment of unconditional compassion at his death and freeing Yoda and Obi-Wan's spirits which further helped him to reach his identity out of the Force.

The procedure of getting turned in to the Blue Ghost spirit can be found in the d20 version of the Star Wars RPG in the supplement book Power Of the Jedi Sourcebook (PotJ). It states that one can retain his or her identity after death only if he has got the immense strength and willingness to overcome the wish of the Force to avoid he absorption of one's consciousness. Its not compulsory that the dead body should vanish to become a spirit.

Jedis of the Blue Ghost do not stand for the exploitation of the Force and hence their spirits gradually diminishes in to the force after a particular span of time. They hold a very strong position in the Force and maintain a very close relationship with those who are living and transform themselves in to Force Spirits to help them with suggestions or guidance in dire circumstances and later on accept the will of the Force and entirely erased their existence. Wikipedia