Korathis - Dragon Riders
The Elite of both Warrior and Political Korathi society, Dragon Riders are revered almost as much as the mounts they ride. They are primarily Dragonborn, though the occasional human is selected. Half-Orcs don't tend to do well as riders, and the other races are considered inferior canditates.
Promising warriors are paired with a young wyrmling shortly after hatching, and are trained together for years. A single dragon or dragon rider lost is a tragedy for the nation.
Once Riders reach a certain age and retire, their dragons can choose to select a new rider or retire with their rider. Tradition dictates what a dragon should have at least 3 riders before choosing retirement, given their longer lifespans, but sometimes they choose retirement early and then fly off to live on Mount Draconis after the death of their rider.
At any given time there are approximately 200-250 Dragon Riders, however only 150 or so are considered 'active'. The remaining retired riders or riderless dragons may answer a call to arms if they feel the need, however the choice is entirely theirs.
Most combat ready dragons are still 'Young Dragons' or early stage 'Adult Dragons' at the oldest. If they live long enough to reach Adulthood, they often tire of mortal issues, and loosing riders, and disappear into the wild.
Because of this, breeding attempts have been made to produce a line of "Drake's" over the years. A shorter lived, but more prodigious reproducer variant of a Dragon, with less intelligence. However the idea is met with everything from general hesitation to outright hostility by citizens who believe that it would be blasphemy to dilute a pure draconic bloodline.