Scintilla
Scintilla is the birthplace of both the Pompous French Assholes and a peculiar walking city. It is also the sector capitol of the Calixis Sector.
Overview
The world is governed by Calixis Sector Governor Marius Hax. It is a thriving Imperial hub that supports the largest planetary population in the territory of around 25 billion. It is dominated by two vast hive cities, Hive Sibellus and Hive Tarsus which hold the majority of the planetary population. Despite the dominance of those two hives, the "offspring" communities, Ambulon and Gunmetal City, contribute significantly to the planet's economy as well. Scintilla is basically pre-Revolutionary France ins SPEHSS; where the powerful and wealthy compete whilst stuffing themselves with cake. It is also the fashion-capitol of the Sector, like Space Paris. This range from the wondrous fashions of the hive's nobility to the spectacle of the hives themselves. Landmarks like Lucid Palace and the Cathedral of Illumination, are famous throughout the Calixis Sector.
Also like pre-Revolutionary France, it is also a world of corruption where instead of one Marie Antoinette, you have like a couple dozen of them. This in turn, creates an atmosphere of unrestrained smugness and the occasional "HON HON HON!". Noble houses consider themselves (sometimes correctly) as above or outside Imperial law and can wield immense influence. Their attitude towards the lower-born is callous; it is not unknown for thrill-seeking degenerates from noble houses to prey upon lesser humans as a sport.
On the other end of the social spectrum, the underhives are rife with mutants, outlaws and ultra-violent gangs, as well as psychotic zealots from the Cult of the Redemption.
The middle hives are trapped between aristo spires and rancid underhives and the hivers live the thankless life of unending toil, where ignorance is a virtue and death a reward for a lifetime of loyal, drone servitude, fulfilling the exorbitant tithes levied on Scintilla by the Administratum. It has been this way since the days of Angevin and some of Scintilla corruption is so deeply ingrained that it is invisible even to those who perpetrate it. Perhaps literally so, given the close ties of the Minor Chaos God Balphomael and its cult, the Brotherhood of the Horned Darkness, to the planet.
Hives Sibellus and Tarsus
The two hives are Scintilla's most important features. The hives are largely independent, ruled by the councils drawn from the nobles of the spires. The majority of the inhabitants of the middle hives are the labouring class, without whom the planet's manufactories and trade houses would cease to function. Almost all middle hivers are owned or indentured to nobles from great sector-wide families or Scintilla's own lesser houses. The most neglected, polluted and crime-ridden areas of the hives are underhives, where life is cheap and brutal gangs fight for supremacy before inevitable violent death claims them. As long as the violence doesn't spill into middle hives, the authorities are happy to let the gangs kill each other in the cesspit of the underhive.
Scintilla's two great hives have always competed against each other for prestige and influence, but no rational observer could fail to acknowledge Hive Sibellus's dominance. It is larger than Hive Tarsus, referred to as "the Capital" or the "ruling hive" and is the seat of both political and administrative power and the centre of the planet's manufacturing might. Hive Tarsus is a dark, shadowy twin of the Hives Sibellus, referred by Sibellians as the "other place" and is a mercantile hive which controls all off-world trade and commerce. Neither hive could function without each other, a fact celebrated in Scintillan proverbs and myths. However, neither great hive could openly admit the importance of "offspring" communities, the aforementioned Ambulon and Gunmetal City, both of which wield considerable influence.