Yen Sid is a powerful sorcerer and teacher of Mickey Mouse, who first appeared in The Sorcerer's Apprentice, a segment of Fantasia. He is also a Keyblade wielder who had fought during the Second Cartoonian War, and had trained many pupils including Mickey during his day, and he, in a way, is what helped Mickey grow in personality since the time he stole his wizard. He is also the watcher of Wasteland who, ever since Mickey accidentally ruined it, has been the only one who knew about the problem, never telling anyone for fear of his position.
Yen Sid is extremely wise and a very strict person. He is best known for his wisdom and skills with magic. Although Yen Sid is strict, he seems to have a sense of humor. Yen Sid cares deeply of Mickey's goal in becoming a great sorcerer and Yen Sid does whatever it takes to make Mickey's dreams come true.
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, which is apparently the source of his power. In the short, Mickey steals the hat and begins to play with its magic. But, 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, proving his mastery of magic is still powerful even without his hat.
Yen Sid reappears in the sequel and lives out the same role in the original. His sequence in the Fantasia sequel being the only sequel from the original film to appear in the film.
Role in the series
Yen Sid is a member of the High Council of Heroes, more specifically, the teacher of Merlin and the original druid army that defeated Chernabog in the First Cartoonian War. He was one of the many members that had greater powers in magic, and is an exceptionally-skilled Keyblade Master who previously trained a few minor pupils, including Mickey Mouse during the time of the Sorcerer's Apprentice short where he needed a lot to learn. Though even to this day, Yen Sid is still an authority figure for Mickey.