Librarians, of course, existed in the legion but they were never well respected until many years after the Heresy. Upon the Primarch's death, the Night Lords were finally forced into the Eye of Terror to join their fellow Traitor legions. There they saw the truth of the galaxy.
If you were going to battle against the powers of the warp, you had to have solders who knew about the Ruinous Powers and could wield their own. To hold his own against the others within the Eye of Terror, Vigo quickly promoted Ming to second in command. They had fought together for along time, and Vigo knew of Ming's special talents. With the shackles of disapproval cast from his neck, Ming delved into the mysteries of the warp. And now thousands of years later, he is the Master Sorcerer of the Sons of Night.
Corruption
Ming never had formal Librarian training, so he had to learn as quickly as he could in desperate, early days within the Eye of Terror. Deep in his meditations, Ming found a voice willing to help him. What he did not know at the time was that the voice belonged to an agent of Tzeentch. Thus began Ming's slow corruption by the whispers of the Lord of Change. At present, Ming believes no one knows of his support for Tzeentch. And he hopes that Vigo remains unaware.
Appearance
Ming wears standard power armor wielding a Force Sword with a Plasma Pistol at his hip. Like several of his brothers in the Sons of Night, Ming wears a robe over his power armor. This harkens back to the Night Lords hatred for the Dark Angels based around the Thramas Crusade. In a further mocking of the Loyalists, Ming wears Purity seals made of skin taken from his victims claimed on the battle field.
Secret motivations
It is Ming who persuaded Vigo to allow Obliterators, Forgefiends, and Defilers into the army. He hopes to slowly change the beliefs of the Night Lords as they concern to the gifts of the Chaos gods. He also wants to expand the number of Sorcerers in the warband.
Ave Dominus Nox
