Soravakhin The Fall of the Onyx

Soravakhin is the Anyatin word for demon.
In the land of Anyat live the Rekonatah, the Longtails, who resemble dragons in face, claws and tail. In every other way, they possess human qualities, and suffer the consequences of human weaknesses.
Anyat is a land governed by the Order of the Onyx; a knighthood called the Tarkha, made up of the sentient Ei-Avakharah, the Gifted Horses, and their Rekonatah riders. This symbiotic, and often telepathic relationship results in a powerful entity, which, favored by the five spirit-gods they call the Akharin, makes for a strong defense and keeps the peace among Anyat's citizens.
Yet, what happens when one of the most powerful members of the Tarkha, a top-level Commander with a genius-level intellect and superior fighting skills, goes against the Council of the Onyx, and even defies the will of the Akharin themselves?
Book One centers around this rogue Commander they call 'Soravakhin', and the consequences therein, if he should be successful in his evil plans.