Belial is Master of the first company Deathwing of the Dark Angels.
Official Canon Edit
Belial is a harsh and stubborn perfectionist who commands the Dark Angels' famous Deathwing company. He had served in the Deathwing under the command of Azrael until the latter's promotion to chapter master, in which he moved out to Company Master of the Third Company. He had many exploits until he was promoted to Master of the Deathwing after the Second War of Armageddon.