The Ancient One was once the master of Stephen Vincent Strange, a.k.a. Doctor Strange, and Karl Amadeus Mordo, a.k.a. Baron Mordo. The Ancient One also activated the mystical abilities of Anthony Ludgate Druid, a.k.a. Doctor Druid. Doctor Druid was one of the Ancient One's first attempts at giving a disciple a degree of his powers. Upon his mortal death, the Ancient One transcended into the spiritual plane, his soul now becoming a minor cosmic entity, occasionally coming to the aid of his former disciple, Doctor Strange.
It was in the hidden village, Kamar-Taj, located along the that the Ancient One was born and raised. The village itself was peaceful. The community lived off the land, unconcerned with the outside world.
However, as the Ancient One grew he and another like-minded villager named Kaluu chose a path different from the rest of their society, one that led them toward the secrets of the supernatural. Together they discovered how to use the mystic energies of the universe.
While the Ancient One wanted to use these newfound powers to help his people, Kaluu could only think of the power it would bring. His friend’s greed caused the Ancient One worry. He was afraid of what Kaluu might do with his newfound powers. However, as the Ancient One spent his time poring over arcane texts Kaluu went about manipulating the villagers through his knowledge of psychic hypnosis.
One day, the Ancient One and Kaluu used the totality of their learned powers to make their village a utopia of sorts. Kaluu then used his influence to take a position of leadership over the village. The Ancient One stayed at his side in the hopes of keeping him in check.
A short time later, bored of the day to day doldrums of Kamar-Taj, Kaluu decided it was time to strike a neighboring village. When he addressed his people with his plans of conquest the Ancient One finally spoke out in defiance. Kaluu’s punishment was swift. He cast an immobilization spell upon him.
The day of the invasion came to pass and the Ancient One was forced to watch in mute horror. The Kamar-Tajians easily overtook the neighboring village and razed it to the ground. With a bevy of slaves at hand the people of Kamar-Taj became gluttonous and lazy. The Ancient One, despite his frozen state, was able to call upon the mystic forces to strike down Kaluu once and for all.
The Ancient One underestimated the results of his mystic attack as it affected the entire village. Disease and pestilence was widespread, crops withered and died, very few people escaped with their lives. Only the Ancient One and Kaluu were unaffected.
The villainous Kaluu soon realized the Ancient One was behind the turn of events despite his immobilized form. He chose to retreat to the dimension beyond the edge of the universe to recoup and harness his mystic capabilities. Before leaving he swore vengeance on his former friend. Once Kaluu disappeared his spell over the Ancient One dissipated and the venerable one was free once more. It was then that the Ancient One vowed to combat evil magic wherever it might be.