During the War of Wrath, an Archduke had several Dukes under his command, who acted as his lieutenants and commanded the bulk of their Legion. Every duke had several hundreds of thousands Fallen under his command, with a near equal number of mortals beneath them. After the Archdukes were summoned by the ancient Babylonian magicians that transformed them into Earthbound, the remaining Dukes are the highest authority left within the Abyss, caught up in their own games and powerplays.
The sheer spiritual mass and majesty of a Duke makes them unable to pass the still small cracks within their abyssal prison. Most Dukes act through their underlings to shape the Fallen policy on Earth, although many lesser demons pose as a returned Duke in order to gain followers and resources.