The gemstones of Iodem are one of many sources of income we consider "important". The duchy is probably one of the region's larger exporters of them.
—Arius Valdayn about House Valdayn's stake in the Titanicus Association
The Duchy of Iodem, sometimes called the Crystalline Duchy or Crystal Duchy and rarely called the Titanicus Duchy, was the government of the Iodem System and some other territories in the Ethereal Demesnes centered around the world of Iodem. It was a member of the Diet of the Ethereal Demesnes with voting representation, representing House Titanicus as an Autocratic Demesne, though it was sometimes unofficially considered an Oligarchic Demesne due to the economic dominance of the Titanicus Association in the Duchy's territories and those protected by it.
Initially, the Ioden state was one of the first of the less-prominent Ethereal Human states to break away from its colonial homeworlds, in Iodem's case being the Kingdom of Luctanem and the Protectorate of Arcuvium. However, the House Titanicus still held the Luctan ruling family, the House of Valdayn, in high esteem. Thus, Iodem quickly became one of the earliest examples of "Valdayn patriotism"; an Ethereal political concept which was based upon having positive attitudes towards and granting favorable dealings to the Valdayns due to their assistance in various matters, both directly and through their significant influence and wealth.
In fact, in time, the Iodem system became one of the Valdayns' significant sources of income; its mines, built to produce crystals and gemstones of various types, suddenly struck what the reigning duke of the time referred to as "the ultimate motherlode". By this time, the Valdayns already had significant political and diplomatic sway on the planet, Luctan military forces defended Ioden borders alongside their own military, and the Valdayns and their favored friends and allies held large numbers of shares in the system's more-or-less monopoly company, the Titanicus family's own Titanicus Association. Following the discovery of the supposed "ultimate motherlode", the Valdayns' interest in Iodem immediately multiplied exponentionally.
By just one generation later, the Valdayns had successfully completed political maneuvers leading to their inheritance of the Ioden throne and economic dealings which resulted in their becoming majority shareholders of the Titanicus Association. From this time on, for over twenty millennia, Ioden gem shipments regularly went to Luctanem for storage or sale, and even when shipped elsewhere, the Valdayns often took their share of the shipment or the profits, and often both. Only during the Galactic Civil War, when the Ethereal Empire was restored, did King Arius Valdayn finally return Iodem's throne to the Titanicus family, and even then, Iodem had long since become so attached to Luctanem that they readily continued supplying their crystals to Luctan markets.