This character is here is something called a "Dreki". It was originally made by  Tsuyukiko a while back, but I have taken my own spin on the species.

Dreki's are a sort of lesser dragon species with black skin and white hair, covered with horns, spikes, and patches of skin that bioluminesce in a variety of colors, usually where any hunks of bone emerge from the skin, as well as on the nose and thighs. As dragons, they also have limited firebreathing ability. They are fairly large, standing roughly 9~10 feet tall, as strong as horses and just as fast.

The easiest way to explain my take on Drekis is that they're sort of like "Yoshi". Thanks to their size, strength, well-developed legs, spinal structure and intelligence, Drekis were once popular choices as mounts, as a sentient mount is much easier to train and Drekis tend to be fairly humble. Things have definitely changed since Drekis were first integrated into the population and now have more rights than mere servants (Though this can change depending on the location).

This Dreki(Currently Unnamed) in particular is descended from a family of Drekis who is still associated with a family of wizards who used to use the Drekis as servants. However, since reparations went smoothly, the two families are still on excellent terms and this Dreki grew up together with the family's youngest descendant, a young man who certainly lives up to the family name(Their parents love to tell the story of when the two first met as babies; she bit him on the head!). She is willing to carry him on her back, not out of servitude or tradition, but because they are such close friends (she enjoys it a bit, actually). The two are still pretty much equals, with the young man's magic being used for healing, protection and making money. She does tend to startle those she meets for the first time when she starts talking, as few expect a mount to be smart enough to talk.

Saddles are all the rage with the young Dreki girls where this Dreki is from, and she is often envious of some of the plush pillows and lacy frills that other Dreki girls carry on their backs (Since she has a rider, she needed a more practical design). Though this doesn't necessarily translate well in other regions where the rights of sentient beings are a more volatile issue.