The Firedragon (Flynn Nightsider, #0.1)

Almost a hundred years ago, the Enchanters defeated the Lord of the Underworld in one of the most fearsome wars the world had ever seen. The public thinks that this victory means the people are safe. But they're wrong. The supernatural beasts the Lord unleashed remain on the earth, multiplying and ravaging what's left of civilization. As long as these monsters exist, mankind will be in danger. And though the government, ruled by the magic-wielding Enchanters, seeks to protect their people, they are too few in number. They need the Defenders - a special class of non-magical humans - to fight the monsters. The Defenders are an elite force, and mankind's only hope against the horrors that live beyond their gates.
Fourteen-year-old Aurelia "the Firedragon" Sun has been training since she could walk to become a Defender, and her extraordinary combat skills have earned the attention of the powerful government. In fact, she's been tapped to represent her nation in an international monster-fighting competition, which pits champions from across the globe against creatures of the Underworld in a violent spectacle. If she wins, she will become a full-fledged member of the Defender force.
But as Aurelia moves deeper into the competition, she realizes that all is not as it appears. There's something sinister behind the competition, something that could change the way she sees everything … and the Enchanters, it seems, are not the heroes she thought. Aurelia begins to ask questions. But before she can discover the truth, she is pitted against the most dangerous monster in the competition - one that will take her life if it can .