The Stone Demon - Karen Mahoney

They say the truth sets you free, but they have no idea how far off base that is. Free? I don't think so. After being tricked into opening the doorway to the Demon Realm by Aliette, the Wood Queen, Donna Underwood is faced with a terrible ultimatum from the newly released demon hordes: the alchemists must deliver the Philosopher's Stone, or the world will be plunged into a devastating modern-day Dark Age. Donna is sent to London, where she can learn how to recreate the Stone and complete her alchemist's training. But time is running out. As she faces Demian, the vengeful demon king, Donna realizes the awful truth about collecting the Stone's elements. And this time, even braving death may not be enough to save the world.