Ventrillia is a ridiculously wealthy world of the Imperium, having lots of rare gemstones that the Adeptus Mechanicus want to get their mechanical hands on for research and manufacturing.
The citizens of Ventrillia also like having lots of gemstones, but in order to get their hands on said gems, first they must withstand a underground, coming-of-age ritual known as the "Trial of the Lava Lakes." If said individual survives the ritual, they will be greatly rewarded with a wealth enough to get the hell out of the Imperial Guard. However, Ventrillia has a proud military culture that streches back to pre-Imperial times and not wanting to risk to give up their commissions, they instead "give" their shiny rocks and whatever wealth they have to the officials of the Departmento Munitorum and Rogue Traders to not get fed into the Imperial grinder, but to go into war zones that are fill to the brim with adventure and glory. The Ventrillian Nobles are equipped with the traditional Ventrillian uniform with helmet, Lasgun and bayonet, and an ancestral duelling sword, quickblade or the heavy Zwei-händer. The Adeptus Mechanicus also provides a steady stream of super-heavy tanks to Ventrillian regiments in exchange for Ventrillia's gemstones.
The Ventrilian Nobles were first mentioned in the Codex: Astra Militarum (8th Edition, page 28)
Notable Ventrilian Nobles Regiments
86th Ventrillian Nobles Regiment, "Carmine Eagles" - One of the better known regiments of the Ventrillian Nobles.
The Ventrillian Nobles uniform resembles that used by early 16th century spanish conquistadors in some aspects, the helmet is similar that of the burgonet used by wealthy spanish conquerors. They also seem to have aspects of the Tileans from Warhammer Fantasy Battle.