Barons were the brigade commanders of the Legions during the War of Wrath. Each Baron had several thousands of Fallen under his command, as well as great geographical territories and mortal servitors. Several hundred Barons were appointed by the time Heaven won the War and banished the Fallen into the Abyss.
Most original Barons are still trapped within the Abyss, but some of the returned Demons have gained the title through sheer political acumen and influence over the modern Courts and mortal agencies. The Courts of Paris, New York City and London are all headed by Tyrants that are also Barons, and while the number of Fallen they command is a far cry to the old times, they are among the most powerful of those Demons that can escape the Abyss.