The Underland Chronicles Series by Chanda Hahn, Rachel Dulude

Long ago, before humans forgot them for all eternity, monsters and immortals retreated below ground to seek shelter. But what do the Greek Gods do when they're bored? They bring back the Olympic games-only a lethal version. The newest contender in these bigger, deadlier games is a young human girl they kidnapped from the streets above. For Kira Lier, it's kill or be killed as she races against beasts she thought were just myths, to cross the finish line and win a chance to earn her freedom.

Kira Lier thought she had escaped Underland and the monsters within, but her freedom was only an illusion, an extravagant lie created by the Underlords to keep her imprisoned. To break free and find Zeke and her friends, she teams up with Allyn, a mysterious young mage with a dangerous past. When a bounty is put on their heads, she becomes the hunted, for the Underlord’s won’t let her slip through their grasp... moreKira Lier thought she had escaped Underland and the monsters within, but her freedom was only an illusion, an extravagant lie created by the Underlords to keep her imprisoned. To break free and find Zeke and her friends, she teams up with Allyn, a mysterious young mage with a dangerous past. When a bounty is put on their heads, she becomes the hunted, for the Underlord’s won’t let her slip through their grasp. She has been chosen by the Fates to save Underland because their world is dying, and their only hope lies in Kira surviving the deadliest game… the Labyrinth. less