Hadross is the instrument of Fate. The Deep Gods have revealed the end of this world, and Scion King Hadross's entire nation is dedicated to bring about this vision. In the world to come, his people rule all that is, so now they move to destroy all they do not rule.
Unknowable eons past, an otherworldly power neither elemental nor god left its mark upon Arikania. Scion King Hadross deciphered these marks and contacted the power they described. Desperate to counter the power of his brother Nasier, Hadross pledged himself and his people to this elder thing, sacrificing himself to save all that he loved.
This bargain transformed his nation of Oserkar and his people. More and more of them are not even remotely human, and the possession of their bodies by servants of their Deep Gods accelerates these changes. They understand, however, that they will inherit the world and preserve its best qualities. How small a price is their humanity weighed against that?
Hadross shall rule all that exists; this is written on tablets predating the elemental lords. His people are the right hand of doom, and they will rebuild the world.