Yen Sid (Earth-101001)

Yen Sid (イェン・シッド, Yen Shiddo) is a powerful sorcerer originally taken from the "The Sorcerer's Apprentice" short in the Disney film Fantasia. He is a retired Keyblade Master, renowned for his wisdom and command over the arts of magic. Although he is no longer an active Keyblade Master, he still keeps a close watch on the balance between light and darkness. He was once Mickey Mouse's master and taught him everything he knows of magic and the Keyblade.

Appearance
Master Yen Sid is a rather severe-looking old man with long, grey hair, bushy eyebrows, and a long, grey beard that parts down the middle. He wears the famous, conical sorcerer's hat on his head. The hat is blue and decorated with several yellow stars and a yellow crescent moon. Fantasia shows that the top of Yen Sid's head is bald under the hat, though he never removes it. He wears long, billowing blue robes with sky blue lining, with the insides of his robes being dark red. The whites of his eyes are quite large in comparison to his small pupils, something that is further highlighted by the fact that his eyes are often wide open.

Personality
While little is known about his life as a Keyblade master, the elderly sorcerer is shown to be a rather stern man. In almost every instance, he is shown to be frowning. But beneath his harsh exterior belies a man who strongly believes in his apprentices no matter how much mischief they may get up to, demonstrated by when he expresses annoyance at Mickey for running off with the Star Shard and recklessly getting lost with it, but then forgives Mickey and awards him the title of Master with an encouraging smile. Despite his outwardly gruff nature, he has displayed a sense of humor, shown when he cracks a smile and points out in a friendly manner how small Sora's clothes have gotten.

Given his past status as a Keyblade master, he is shown to have great knowledge about the properties of the Heart, the Heartless, the Nobodies, the Unversed, and the Dream Eaters. It is he who explains the nature of the Unversed to Master Eraqus, and that of the Nobodies and the Dream Eaters to Sora, Donald, and Goofy, and also tells them that as long as darkness exists in one heart, the Heartless will never cease to exist. So powerful and wise is he, that even Terra, Aqua, and Ventus speak to him with utmost respect, despite him not being their master. However, Mickey and Riku merely refer to him as "Yen Sid" without calling him "Master", possibly because they, like Master Eraqus, are also Keyblade Masters (though this is only in the English versions; in the Japanese versions, they still call him "Master Yen Sid" as a sign of respect).

Past
Yen Sid was once a Keyblade Master alongside Eraqus and Xehanort. He chose to retire to the Mysterious Tower and lay down his Keyblade Master mantle, but remained a powerful sorcerer and continued to observe the balance between light and darkness. He also hoped Xehanort would let go of his fascination with the Keyblade War and the χ-blade.

Yen Sid took on the boatman Mickey Mouse as his apprentice, teaching him everything he knows about magic and the Keyblade. At one point, he sent Mickey on a mission to the Country of the Musketeers.

However, Yen Sid was unable to give Mickey a Mark of Mastery exam. After saving Princess Minnie, Mickey had decided to end his training and instead focus on being king of Disney Castle.

Kingdom Hearts Birth by Sleep
Yen Sid had become aware of the presence of the Unversed threatening the worlds, just as his former apprentice Mickey had. Mickey returned to Yen Sid to complete his training as a Keyblade Master. Believing Eraqus and Xehanort could use the help of another Master, Yen Sid resumed completing Mickey's training. However, after Mickey failed his first test, Yen Sid told him of feelings of dread he had; something terrible would occur soon. The next day, Yen Sid contacted the Land of Departure to warn Eraqus of the threat and to send his pupils out to quell the chaos. Mickey decided to assist without permission and stole a Star Shard to travel the worlds; because Mickey did not fully understand how it worked, Yen Sid remained unable to track him as the shard randomly sent Mickey around the worlds.

When Terra visits Yen Sid's tower, he asks him for guidance about Master Xehanort, Vanitas, and the Unversed; Yen Sid advises Terra to treat all three as the same problem. After Terra leaves, Yen Sid muses on his disappointment in Xehanort's continuing folly. Later, Ventus shows up at his tower with a Star Shard, and Master Yen Sid uses divination magic to locate Mickey. However, unforeseen interference prevented Ventus from returning with Mickey. Aqua later returns Mickey to his tower, and Master Yen Sid tells her of Master Eraqus's destruction and that the murder was committed by Terra and Master Xehanort. Sometime after Aqua leaves for the Keyblade Graveyard, Mickey departs to assist her and her friends.

Following Vanitas's defeat, Mickey returns with Aqua and a comatose Ventus. Master Yen Sid finds himself unable to sense Ventus's heart and encourages Aqua to believe in their friendship, which serves as the key to bring him home one day. Sometime later, Mickey sorrowfully hands in the Star Shard and his Keyblade, thinking he has failed his Mark of Mastery exam and disgraced his master, and prepares to depart. However, Master Yen Sid gives him back the Keyblade, showing that Mickey, in fact, passed and became a Master.

Kingdom Hearts Next Generations
Yen Sid serves as Sora's tutor to what lies ahead of him in his journey. When Sora and company (Donald Duck and Goofy) arrive, he tells them of the enemies that they will face in the near future (Heartless, Nobodies, and Organization XIII). He also returns their Gummi Ship to them, which he had been safekeeping, and sends them to Hollow Bastion.

When Diablo brings Maleficent's cloak to Flora, Fauna, and Merryweather, causing her to be revived, the fairies rush off to tell Yen Sid. However, by the time Sora and his friends can return to the tower, Yen Sid and the fairies are nowhere to be found.

Blank Period
After discovering that Sora has the power to save all the lost hearts connected to him, Mickey meets with Yen Sid to discuss their ongoing search for Terra, Ventus, and Aqua. However, Yen Sid shocks Mickey by revealing that the destruction of Ansem and Xemnas has led to the return of Xehanort, and not just a "single one" of him, and which will eventually lead to the return of Master Xehanort. Yen Sid had known that this disaster might come about while he was mentoring Sora, but chose not to disclose it to anyone because leaving Xemnas alive was not an option. As Mickey, the sole surviving Keyblade Master, will not be enough to counter Xehanort's new threat, Yen Sid orders Mickey to summon Sora and Riku to him to undertake the Mark of Mastery exam.

Kingdom Hearts Dream Drop Distance
Yen Sid explains the full history of Master Xehanort to Sora and Riku and puts them through the Mark of Mastery exam by assigning them to awaken several worlds which remained in a state of "deep sleep" following Ansem's destruction, and explains numerous facts such as the nature of the Dream Eaters and residents of the sleeping worlds. However, soon after the exam begins, Yen Sid starts to feel that something is going awry.

Later on, when Mickey, Donald, and Goofy depart for Disney Castle to confront Maleficent, Yen Sid surmises that the growing darkness in the worlds due to Master Xehanort's coming return may be the reason Maleficent has become strong enough to resist the Cornerstone of Light. The trio soon returns with the revived Lea, who requests to become a Keyblade wielder. Yen Sid, taken aback, warns Lea of the dangerous path ahead and has him undergo a magically compressed training session under Merlin and the three fairies. Eventually, when Sora and Riku do not return from the Sleeping Worlds as planned, Yen Sid realizes that Xehanort devised a means to confront the two in the Sleeping Worlds and sprung a trap on them. He allows Mickey to make his way to The World That Never Was to save their friends, sending Lea, Donald and Goofy after Mickey as back-up.

Mickey and the others eventually bring Sora's comatose body back to the study, where Yen Sid realizes that Master Xehanort was on to them the entire time. When Riku awakens Sora from his slumber, Yen Sid delivers a sincere apology to both of them for failing to realize the magnitude of Master Xehanort's plans. Though he commends them both for performing admirably, Yen Sid only declares Riku as a Keyblade Master, since he managed to unlock two Keyholes of Sleep, while Sora failed to resist the darkness and ended up in a magical sleep induced by Young Xehanort. Yen Sid, however, is visibly stunned when Lea finally manages to summon his own Keyblade.

Having realized Master Xehanort's plan to recreate the χ-blade by pitting his new Organization XIII against the seven Princesses of Heart, Yen Sid devises a plan to counter Xehanort by gathering seven Keyblade wielders of Light to protect the Princesses, and orders Riku to bring Kairi to him to undergo training with the Keyblade she received from Aqua.

Kingdom Hearts Guardians of Light
Shortly after Kairi's arrival, Yen Sid informs her, Riku, and Mickey of their objective to rescue Terra, Ventus, and Aqua from their fates. He has Mickey inform Riku and Kairi of what happened to Aqua following her fall into the Realm of Darkness. After Mickey explains Aqua's current whereabouts, Yen Sid explains that the real reason why Mickey kept the news a secret was to prevent anyone from entering the Realm of Darkness before it was safe to do so. He grants Riku and Mickey new garments from the three good fairies to shield them from the darkness and assigns Kairi to train with Lea under Merlin's tutelage in the ways of the Keyblade.

Soon after, Sora returns from the Sleeping Worlds and is instructed by Yen Sid to find a way to restore lost hearts. Yen Sid reminds Sora that the boy has lost his abilities once more and directs him to Olympus Coliseum to train with Hercules.

Yen Sid guides Sora on his quest to obtain the power of waking, while Riku and Mickey venture off to rescue Aqua.

Powers and Abilities
Master Yen Sid is a master of the magical arts, able to perform powerful magic spells comparable to Merlin's. He has shown the ability to teleport, create illusions while training Mickey, and create cosmic smoke to locate a person. He seeks counsel with the stars to predict the conditions of the present and the future, which allows him to gather information about the worlds' condition and to pass it on to his allies.

He has also shown the ability to manipulate and utilize the power of light to an extraordinary extent, as demonstrated at the Keyblade Graveyard, being able to part an immense army of heartless with a mere gesture of his hands and hold them off long enough to allow the guardians of light to advance through them without any exertion.

As a retired Keyblade Master, he presumably still retains the power to use the Keyblade but does not appear to use it.

Origin
The great sorcerer first appeared in the Fantasia short The Sorcerer's Apprentice as Mickey Mouse's master. He was the owner of a magical hat that is apparently the source of his power. In the movie's most acclaimed sequence, Mickey steals the hat and begins to play with its magic. However, as he was warned by Yen Sid, the power of the magic cannot be controlled by Mickey and wreaks havoc. Yen Sid arrives and manages to stop the magical chaos with his own powers.

His name is "Disney" spelled backwards, as a tribute to Walt Disney himself.