The stone demon - Mahoney, Karen (Corgi Books, 2013)
Forts. von: Mahoney, Karen: The Wood Queen. - "In order to produce the Philosopher's Stone, as the demon hordes demand, alchemist apprentice Donna Underwood pits her unpredictable powers against a vengeful demon king, two maleficent faery queens, and an immortal magus with his own shadowy agenda"-- Provided by publisher.