Gilded #2 Cursed (hardcover) Marissa Meye

Before the Endless Moon, when the Erlking means to capture one of the seven gods and make a wish to return his lover, Perchta, from the underworld, Serilda and Gild attempt to break the curses that tether their spirits to Adalheid's haunted castle. But it soon becomes clear that the Erlking's hunger for vengeance won't be satisfied with a single wish, and his true intentions have the power to alter the mortal realm forever. Serilda and Gild must try to thwart his wicked plans, all while solving the mystery of Gild's forgotten name, freeing the ghosts kept in servitude to the dark ones, and trying to protect their unborn child.