Oriana Personality: optimistic, freedom-loving, good-humored, honest, straight-forward, intellectual, blindly optimistic, tactless, restless, impulsive, risk-taker, kind-hearted, caring, adventurous, confident, arrogant

Nubia Personality: protective, intelligent (about as smart as an orca), loyal, obedient

Oriana is a princess who ran away from her kingdom because she didn't like how the king and queen (her parents) and siblings and all beneath them (knights, particularly) all wanted to hunt and kill dragons, just for sport or to "protect the kingdom," even when the dragons would seldom attack.
She was interested them since her youth, but instead of wanting to kill them and fear them, she'd always been fascinated by them and wanted to know more. So, when the opportunity came up for her to leave and start protecting the few remaining dragons, she leapt to it, taking her skill of sword fighting with her (which she'd learned from her older brothers).
Her very first rescue was Nubia. The wingless dragon had migrated from some eastern land, and her (the dragon) stunning gold scales would fetch a high prize. Oriana stopped a knight from killing the dragon, and in thanks, the dragon flew off with her, leaving the knight dumbfounded.

Nowadays, knights and other would-be dragon hunters know her name and the threat she brings to their business. Knights who see her have been instructed to bring her back to her parents, but random dragon hunters are much less likely to be lenient. Fortunately, she has her sword and Nubia to protect her, and the two go around saving dragons (and sometimes other mythical beasts) from certain death.

Nubia doesn't breathe fire, but she can spit up hot water at foes and hold her breath under water for a long time. She can fly, too, but she tends to prefer ground travel. She and Oriana have grown close, and she gets antsy every time Oriana must leave her to gather supplies. Despite that, she's obedient and loyal, and if Oriana tells her to stay somewhere, she does so and will wait for days for Oriana, if needed (unless she hears she's in trouble, in which case, she's off instantly to help out).