Source: Campaign Setting, pg(s). 115
Castle Urion is the first city most crusaders heading to Mendev (and from there to the Worldwound) see when the enter Numeria but it is far from the typical barbarian settlement that are strewn across the country. This settlement is technically under the control of the Black Sovereign but it is in reality controlled by it founders an order of knights dedicated to Iomedae. These knights built Castle Urion as a way to protect and guide those crusaders sailing up the River Sellen (or "River Road" as it is often called) from Cassomir in Taldor to Chesed. This order of Iomadae knights is particularly special as they ride trained griffons which help them patrol vast stretches of the river, certainly more than they could if they patrolled only on horseback.