Nemesis

It's hard to defend the Earth from deadly monsters when you suspect you might be one of them.<br><br>Discovering she's a walking magical weapon is just the beginning of Ada's problems. Her guardian thinks she's turned traitor and her new boss has put her on goblin-catching duty. With enemies around every corner and a centaur uprising threatening to bring a bloodbath to Earth's doorstep Ada and Kay are once again thrown into danger -- and a conspiracy that could change the world as they know it.<br><br>Against an enemy they quite literally can't see Ada and Kay must face up to the real deadly potential of magic...