Lord Sunday (The Keys to the Kingdom)

The fantastic conclusion to Garth Nix's NEW YORK TIMES bestselling series!

The House is falling apart, and when it is destroyed, all existence will be destroyed with it. Arthur Penhaligon and his friends Leaf and Suzy must use every power at their disposal - magical or practical - to defeat the enemies attacking them from all sides.
For Arthur, the most formidable challenge comes from Lord Sunday, the most elusive of the Trustees of the Will. Lord Sunday's magic is unlike anything Arthur has encountered before - and his secrets have the potential to destroy not only Arthur, but also all the people he holds dear.