Harmonium

("Hardheads"), who believe that peace and stability can only be established under one rule — theirs. The planar faction known as the Harmonium is actually just a small part of a much larger political entity which rules over the entirety of the Prime Material world of Ortho. In Sigil, they serve as the city's police force, and their headquarters is the City Barracks. It is strongly advised that visitors to Sigil never, under any circumstances, use the term 'Hardhead' in front of Harmonium members.