Eternal Knights of Eden I - Alexander Scott Guinn - Bog

Thousands of years ago on the planet Eden, a war between two godlike beings devastated the nation of Temenos and wiped out its people, the Mitera. Ever since, a corrupting miasma has threatened the land, turning nearby inhabitants and beasts into grotesque, violent forms.
When Shaide Darkmoon, one of the last Mitera, loses his parents to the corruption, he is forced to leave his best friend, the shy elven girl Amari, and begin training as a soldier in the human army.
All he wants to do is survive, but through a twist of fate, he will come to wield a power of unimaginable strength.
This power will be needed like never before, for a darkness is rising in the ruins of Temenos, and it will not stop until its corruption has spread to every corner of Eden.