Gabriel has been the Grand Master of the Deathwing, the 1st Dark Angel's Company for over two centuries. As such he commands all the Terminator armour equipped Marines in the Chapter, all of the Chapter's Land Raiders and a number of the ancient Dreadnoughts. He also has nominal command of many of the Chapter's veteran sergeants, who have been inducted into the Deathwing but are currently providing their skill and experience to the Battle Companies.
Gabriel is one of the highest ranking individuals within the Chapter's Inner Circle and has a knowledge of the Fallen only surpassed the Supreme Grand Master of the Dark Angels, the Chief Librarian of the Chapter, and some of the older Interrogator-Chaplins. He has personally led numerous "Hunts" and has on three occasions participated in the capture of Fallen former comrades. This, in over five centuries of fighting his Emperor's foes.
An exceptionally skilled fighter, a trusted and beloved leader, and a strategic master, Gabriel has perfected Deathwing company tactics. On numerous occasions he has decisively ended long-winded campaign by teleporting the entire company into the middle of a strategic, well-chosen battle, overwhelming the enemy through sheer impact of having over one hundred Terminators, with supporting Dreadnoughts smashing through their rear areas and headquarters units.