The Creature In The Case Abhorsen Series, Book 3.5.

The Creature in the Case delves deeper into New York Times bestselling author Garth Nix's Old Kingdom. Fans of Rae Carson, Kristin Cashore, Scott Westerfeld, and Cassandra Clare will be enthralled by this rich fantasy world. Nicholas Sayre has just fought off the Destroyer and is eager to return to the Old Kingdom. The only thing standing in his way is a party organized by his powerful uncle. But when he arrives at the party he finds a house ful...