Yoda was a legendary Jedi Master and stronger than most in his connection with the Force. Small in size but wise and powerful, he trained Jedi for over 800 years, playing integral roles in the Clone Wars, the instruction of Luke Skywalker, and unlocking the path to immortality.
Yoda returns as a younger version of himself in the prequel trilogy beginning with The Phantom Menace. 35 years before The Empire Strikes Back, Jedi Master Qui-Gon Jinn brings the young Anakin Skywalker to the Jedi Council. Qui-Gon is convinced that Anakin is the "Chosen One" of Jedi prophecy who will bring balance to the Force and requests the boy be trained as a Jedi. Yoda senses great fear in Anakin, especially in regards to his attachment to his mother Shmi, and foresees "grave danger" in his training. The Council, led at the time by Yoda's former padawan Mace Windu, rejects Qui-Gon's request.
When Qui-Gon is mortally wounded in a duel with Sith Lord Darth Maul, his dying request to his Padawan Obi-Wan Kenobi is that Anakin is trained as a Jedi. Obi-Wan, determined to fulfill his promise to his master, tells Yoda that he will train the boy, even without the Council's approval. Yoda makes Obi-Wan a Jedi knight and reluctantly gives his blessing to Anakin's training.
Yoda, now indirect control of the Order's policy as Master of the High Council in addition to his traditional position as Grandmaster, is one of the many Jedi who are concerned about the emergence of the Confederacy of Independent Systems, a secessionist movement wanting independence from the Galactic Republic. After the first attempted assassination of Senator Padmé Amidala, Chancellor Palpatine suggests that she be put under the protection of Obi-Wan, who is training Anakin. Yoda arrives in time to save Obi-Wan and Anakin from the Separatists and defeats his former apprentice, Count Dooku, the Separatists’ leader, and a Sith lord, in a lightsaber duel.
Yoda leads the Jedi Council in pursuing the mysterious Sith Lord Darth Sidious. Palpatine has by then amassed near-dictatorial emergency powers and begins interfering in Jedi affairs by appointing Anakin as his personal representative on the Council. The Council grants Anakin a Council seat but denies him the rank of Master, feeling that doing so would amount to giving Palpatine a vote in the Council. Additionally, they order him to spy on Palpatine, whom Anakin considers a friend and mentor.
Anakin seeks Yoda's counsel about his prophetic visions that someone close to him will die. Yoda, unaware that the person whom Anakin speaks is Padmé, or that she is Anakin's wife and pregnant with his child, tells him to "train yourself to let go of everything that you fear to lose." Unsatisfied, Anakin turns to Palpatine, who then reveals himself as Darth Sidious. Sidious manipulates the young Jedi into becoming his Sith apprentice, Darth Vader, with the promise that the dark side of the Force holds the power to save Padmé from dying in childbirth.
Sidious later transforms the Republic into the tyrannical Galactic Empire, proclaiming himself emperor for life and ordering the clone troopers to kill their Jedi generals. Yoda is on Kashyyyk, overseeing the battle between the Separatist forces and a combined command of clone troopers and Wookiees. Through the Force, Yoda feels the deaths of each of the Jedi as they are assassinated by their own troops. After swiftly killing the clone troopers instructed to kill him, he escapes with Wookiee leaders Tarfful and Chewbacca to Coruscant, where he and Obi-Wan fight their way into the Jedi Temple to stop a trap for all surviving Jedi. Inside, they discover that all the Jedi inside, younglings included, have been slaughtered. They then discover a holographic recording revealing Vader as the assassin. Yoda decides to face Sidious, sending Obi-Wan to kill Vader. When Obi-Wan protests, Yoda tells him that the Anakin he knew no longer exists, having been "consumed by Darth Vader."
Subsequently, Yoda battles Sidious in a lightsaber duel that damages the Senate Rotunda. In the end, neither is able to overcome the other, and Yoda is forced to retreat. He goes into exile on Dagobah so that he may hide from the Empire and wait for another opportunity to destroy the Sith. At the end of the film, it is revealed that Yoda has been in contact with Qui-Gon's spirit, learning the secret of immortality from him and passing it on to Obi-Wan.
Yoda is also instrumental in deciding the fate of the Skywalker children after Padmé dies in childbirth, recommending that Luke and Leia be hidden from Vader and Sidious; he sends Leia to be adopted by Senator Bail Organa of Alderaan, and Luke to Vader's stepfamily Owen and Beru Lars on Tatooine. Other than the ancient Jedi Master, only the Organas, the Lars family, R2-D2, and Obi-Wan know of their true identities.
30 years after Yoda's death in Return of the Jedi, Yoda's voice is heard by the young scavenger Rey in a Force vision after she discovers Luke Skywalker's lightsaber under a castle owned by Maz Kanata.
Yoda appears to Luke as a Force spirit as he debates whether to burn down the tree storing the Sacred Texts of the Jedi.[21] As Luke makes his way to the tree, Yoda appears behind him and reminds him that a Jedi must always be sure of his path. When Luke decides to burn down the tree, Yoda summons a lightning bolt and sets it ablaze. When confronting Yoda as to why he did it, Yoda assures Luke that the books contained no knowledge that Rey didn't already possess. He stressed that true Jedi knowledge was not found in books but within Jedi themselves--and it is their responsibility to pass that knowledge on, reminding him, "The greatest teacher, failure is." As Luke takes in the message, he shares a quiet moment with his former master, who informs that the burden of all masters is being surpassed by their students.
May the Force Be With You.