The Keys to the Kingdom is a fantasy–adventure book series written by Garth Nix, comprising seven books published between 2003 and 2010. The series chronicles the adventures of a boy named Arthur, who becomes involved with a magical world called the 'House'; he is on a quest to take back the House from seven antagonistic 'Trustees'. Story Plot Arthur, a young boy, has a severe asthma attack one day as two mysterious people, one of which is called Monday, give him a 'Key', a magical artifact that saves his life, against Monday's intentions. He discovers there exists a world called the 'House', which is split into seven parts, each ruled by a 'Trustee', of which Monday is one. A divine being known as the 'Architect' has disappeared and left behind a 'Will', leaving the House and the seven Keys to her seven Trustees, but the Trustees have split up the Will and hidden the parts, intent on not letting the Will be fulfilled. The first part of the Will has managed to break free and, by convenience, has chosen Arthur as the 'rightful heir' who must recover the other lost parts of the Will; this has led to Monday giving up half of his Key to him. In the first book, Arthur defeats Monday and takes control of the first part of the House. Books two to five follow a somewhat regular pattern: in each, Arthur tries to gain control over one part of the House, and ultimately succeeds after various challenges, setting free one part of the Will. Each book features one main antagonist, usually the Trustee of that part of the House, with the exception of one Trustee who wants the Will to be fulfilled but has been overthrown by the other Trustees. Sometimes, the Trustees sow chaos on Earth while he is away in the House. One important recurring part of the story is Arthur limiting his use of the powerful Keys, as using them too much will turn him into an immortal, and the presence of an immortal on Earth causes harm. At the end of the sixth book, Arthur has freed the sixth part of the Will but not yet claimed that part of the House, and the sixth Trustee is busy invading the domain of the seventh Trustee. In the seventh book, Arthur ultimately manages to free the last part of the Will, but