(@chronicallylatetotheparty asks should be turned on now!)
To answer your question: Yes! Legacy does in fact ride a Fearhost. It's one of the reasons she came to be the most feared sorceress in the No-Lands.
The lesser gods and spirits which were corrupted into Fearhosts are less dangerous than major gods. Before the Awakening they were closer to the mortal plane - meaning that mortals can look upon them without too much stress to the mind.
After the Awakening, the destruction wrought upon the world left a power vacuum. Millions died, including powerful figures and royalty. People began clamoring to fill their places, and one way they did this was harnessing the power of minor Fearhosts. These could be tamed by exceptionally strong-willed individuals. Keep in mind, this was not easy; many died in the attempt. All Fearhosts are wild, terrifying, and unpredictable.
This also means that most of the 'royalty' in present-day Vumaya has no true royal blood. Once the new rulers were established, they used their Fearhosts as tools to control others. These monsters were passed on to their children and soon became twisted heirlooms. Not all royal families had them.
This is Duwira, Legacy's mount whom she found in the No-Lands near Pruizau. She is a former desert spirit turned Fearhost, and there are many legends about her taking the lives of lone travelers. She is a being of sand, blood and bone. Her approach is heralded by sandstorms and the scent of decaying flesh.
Below is a size comparison chart.