Armageddon's Ward

"Lia Rector spent her childhood devoid of magic - no easy life for the sole heir to the largest magical corporation in the world. Then Armageddon comes for her on her seventeenth birthday. Her new guardian hides her from the dark magicians determined to take what is hers. Now Lia is racing against the clock to discover the key to her magic before she loses everything in an arena full of her greatest enemies. She knows it wouldn't really be the end of the world if she fails. Just her life"-- Amazon.com