When the injuries he sustained in a horrific accident ended Stephen Strange's career as a surgeon, he made a vow that he would find a way to heal his hands, no matter what the cost.
In the mountains of Tibet, he discovered a mystic known only as the Ancient One. In addition to having his hands healed, Stephen became his apprentice and learned the mystic arts, vowing to become a protector of this dimension. After the death of the Ancient One, the title of Sorceror Supreme was bestowed upon Stephen, making him the ultimate protector of this realm against all things mystical and evil.