The Regenters are an extremist group within the citizenry of the Empire of the Isles that seek to return the Empire to the authortarian rule once imposed by the former Lord Regent, Hiram Burrows. They idolize the former Royal Spymaster and view his arrest as "unjust", actively celebrating the anniversary of his ascension to power and even on occasion wearing armbands depicting the Lord Regent's crest. They are ardent opponents of the Kaldwin dynasty's rule, and have even gone so far as to attempt to assassinate Emily Kaldwin, an attack that failed miserably largely thanks to the combined efforts of both the young Empress and her faithful companion, Alexi Mayhew.
The Regenters apparently rose to prominence roughly four years after the events of Dishonored, as Empress Emily Kaldwin was fourteen years old when they first made an attempt on her life. As detailed in the book The Child Empress, the Regenters ambushed the carrige that Emily and Alexi were riding in while it was trapped between two gates, firing pistols and one attacker even lobbing a grenade at the pair. Luckily, Alexi managed to grab the grenade before it detonated and lobbed it back at the Regenters, and together the two girls managed to fend off their assailants long enough for the City Watch to arrive and secure the area.
This attack had the unintentional effect of increasing the young Empress' standing amongst the people, and also helped propel Alexi Mayhew into the ranks of the City Watch. To this day it is considered a "definitive moment" of Emily's reign.
The ranks of the Regenters appear to be made up of members of the Empire's common citizenry. They do not appear to have a centralized structure, but the book Gathering of the Regenters seems to indicate that their members periodically gather together to discuss recent events and propose new courses of action. Known members of the Regenters include Correy Brockburn, Janice Tines and Teodoro Benitez.