This time the castle is the monster!

Obsidian Ridge hasn't been seen in Faerun for hundreds of years. It's a legend, a fairy story--until it appears, silently and without warning over the kingdom of Erlkazar, blotting out the sun. Steered by the madness of a cunning wizard, the citadel and its vast array of shadowy monsters will destroy all of Erlkazar unless the wizard gets what he wants: the princess of Erlkazar as a bride. But he'll have to battle the king's personal assassin, a loyal courtier, a complicated killer, and the princess herself to bring his plan to bear.