The Shadow Games - The Shadow Academy, #1

Powers make her an outcast. Fear will get her killed. At eighteen, Vesper is driven by one ambition-to live up to her family's expectations and win a place at the Royal Academy. But when she fails an unexpected test, Vesper is taken from the white tower of New Vegas and dumped on the city floor-home to those the city outlaws. She quickly finds herself branded a slave in a shadow city where factions war and monsters terrorize the streets.
Most terrifying of all are the powers that Vesper and her new friends wield. Having killed once, Vesper is determined it won't happen again. To save her friends, Vesper must learn to control her power. And that means facing her greatest fear-that her power could destroy her.