Around 5700 BC, Agamotto forms the Masters of the Mystic Arts as a league of magic practitioners, dedicated to learning Magic so as to safeguard the Earth from dimensional evils.
The Ancient One is born.
In Kathmandu, Nepal, the sorcerer Kaecilius and his zealots enter the secret compound Kamar-Taj and steal a few pages from an ancient, mystical text belonging to the Ancient One, a longlived sorcerer who has taught every student at Kamar-Taj, including Kaecilius. The Ancient One pursues the traitors, but Kaecilius and his followers escape.
Around the same time, famous neurosurgeon Dr. Stephen Strange suffers major nerve damage to his hands in a car accident and spends several months recovering. No longer able to perform surgery, Strange begins a desperate search for ways to heal himself.
Stephen Strange finds out about Kamar-Taj and travels to Nepal, where he spends the year learning sorcery from The Ancient One. Strange learns that The Ancient One has lived for centuries by tapping into the power of an ancient godlike being from the Dark Dimension called Dormammu.
Soon after, The Ancient One is killed by Kaecilius, who seeks to allow Dormammu to take over Earth and end death. Strange defeats Kaecilius by locking Dormammu in a time loop using the Eye of Agamotto, which is actually the Time Infinity Stone, convincing Dormammu to cease his attack on earth in exchange for being released.
Strange then takes up residence in the New York City as the city’s master of the mystic arts with the help of his teacher and fellow master Wong. Strange begins cataloging all supernatural and magical threats to the earthly realm.
Karl Mordo, once Strange’s friend and magical mentor, is disillusioned by The Ancient One’s violation of "natural law" and leaves, later vowing to wipe out all unsanctioned sorcery.