Succession In The Lyceum
Before the time of the Reckoning, every single city-state in the South claimed completely independence, with references to an old, mostly forgotten name before the 'Lyceum' as 'The Hundred Warring Kingdoms of the Southern Reaches'. During the time of the Reckoning, as the south was invaded, a great meeting was called by the heads of all the heads of the southern houses called the Conclave of the Lyceum, a secretive meeting behind closed doors where the southern leaders decided who among them should speak for the south in King Alar Grayson's new Compact he was calling in Arx. House Pravus of Setarco claims it had the first Grand Duke and Duchess of the Lyceum, but the details of this are lost to time, and a half-dozen other houses make the same claim, with it being known that House Velenosa rose to dominance and seized the title through war, treachery or marriage in the decades following the Reckoning.
The title of Grand Duke/Duchess of the Lyceum, and the associated Archduke/duchess of their city-state, traditionally passes through absolute primogeniture without contest. Nor is it anything like a right to bring a contest and demand a conclave- it simply is not done unless the current great house is in no position to contest the call. So while very rare, and often generations going by without a conclave, it is not without precedent.
The title of Grand Duchess of the Lyceum has changed numerous times through the history of the Lyceum, though not since the end of the Crownbreaker Wars. While the details of a Conclave of the Lyceum are extraordinarily secretive, save that it is not in any way an election, a conclave has never been called save when the great house holding the title has been defeated in war or been shown to be clearly, demonstrably weaker than a house claimed as a vassal, with a majority of other ducal houses all in accordance that is the case. On at least two occasions before the Elven War, conclaves have ended with the complete massacre of all visiting noble heads of house, with the grand duke or duchess making an unambiguous statement that they were not as weak as might have been assumed, and holding control for another generation or two. For this reason, conclaves are typically called only when the Grand Duke or Duchess of the Lyceum is completely helpless to prevent the outcome, such as when terms are dictated in their palace for their surrender after a lost war.