Ajdavaan was the ancient city, named after its Architect Alexi Ajdavaan, that was home to the Conspirators. The city rests upon a great monolith of basalt. It is referred to as the City of Doors because walking through a door would not necessarily get you to the next room unless you had the ability to control the doors or were escorted by one who did. Each Conspirator was a Councilor of one of the 13 Districts of the city, and the one we know as the Devourer was the city's Mayor and the 14th on the City Council. The Councilors practiced their particular flavors of evil in mostly secret, and the populace turned a blind eye as best they could because they could not stop their Councilors as they were aligned with demons and horrible powers. Thus they were able to maintain control of their districts even though occasionally a person would just 'disappear'.
The Councilors created the trolls to serve and maintain the city. Due to the nature of the city, Door Trolls were needed to guide most people through parts of the city. Even the trolls did not have unfettered access to the deeper sanctums of the city.