Hidden in the amethyst is the second book in the Amelia Maylock series.
Had the old hag made a mistake? This couldn't be what Amelia was supposed to meet here, could it? Why would she send Amelia to fight such a - whatever it was - without warning her first? Amelia didn't have time to worry any longer as the creature took another giant step forward, looming closer and lowering its huge head towards her, revealing its bright white eyes, sitting in slits in the skull. The light from the orbs at the side of the room glistened off of the black bone, but it couldn't make the creature look anything other than terrifying.