When sorcerers were introduced in the Marvel Cinematic Universe, it opened up a whole new layer of potential to the franchise that could only be explored through the eyes of Doctor Strange. Being that his movie was an origin story, it also meant that Strange would have to encounter beings more powerful than him to learn from. This led him directly into the path of the Ancient One, who was such a mystery that even her name students didn't know her name. Nevertheless, she was a powerful ally in the battle against darkness, despite some faults that nearly doomed all sorcerers.
Source：https://www.cbr.com/ancient-one-terrible-teacher-doctor-strange/
