Just Special Horses

Wyverns come in five common types: feathered, furred carnivore, furred omnivore, fanned, and scaled. The only type not seen in the wild is scaled, which is a deeply inbred population of tamed wyverns that are used a special horses by powerful and rich humans. As a smaller and more manageable species than their cousin species the dragons, wyverns are much more attractive for their uses as guard dogs, warhorses, war machines, and capital-S statement carriage-pullers. However.

Something else that differentiates wyverns from their cousins is their intelligence, a trait that, while generally higher than in the bigger, meaner, and more powerful dragons, is still recessive. Did you know that recessive genes are more likely to manifest in an inbred individual? This usually applies to recessive genetic diseases or ailments, but with careful population management the humans have accidentally created a line of (mostly) disease-free human-level intelligent wyverns.

And they won't stand for this subjugation of their species any longer!

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aka this is an excuse for both a dragon story and a high level of worldbuilding for funsies! Plot hook above currently only applies to Ozy, the others are just there because their chars use parts of the lore I built for the wyverns.