Lord Sunday

Lord Sunday is the final book in the 'Keys to the Kingdom' series, written by Garth Nix. It reaches the conclusion of Arthur Penhaligon's crusade to obtain the 7 Keys to the Kingdom, and continues where Superior Saturday leaves off. During this book, Arthur finds himelf in the Incomparable Gardens, with Lord Sunday and Saturday, fighting each other and Arthur.

Lord Sunday (Character)
He is the eldest son of the Architect and the Old One (who are revealed to be the same people) and the holder of the greatest Key, the seventh Key to the Kingdom with paramount powers in the House and in the many Universes outside of it. This makes him the most powerful being in creation, apart from the Architect, the Old One (we can assume) and King Arthur (when he has all of his powers). Like all of the Days, he is infected with a sin - the strongest sin of all: Pride or Hubris (it is unconquerable becase any act is done for the good of themselves, not others).

Two of the main antagonists in this story are Lord Sunday and Superior Saturday, two of the seven Days against whom Arthur must face off. They were seven of the Architect's favourite Denizens and were placed in charge of the House (in absentia). They were each given one of seven Keys, and the House split into seven Domains, each Day ruling one of these Domains - having absolute power in their Deminse. They were also forbidden to enter the Universes outside of the House (the 'Original Law') but they and their monions are capable of going to any place in existence on the day with their namesake (i.e. 'Mister Monday' can go to Earth on a Monday). Unfortunately, though originally pure of heart, absolute power corrupted them, in different ways, absolutely. In the case of Lord Sunday, he has the sin of 'Pride' or 'Hubris' - extreme arrogance.

Plot
SPOILER ALERT: Plot Revealed.

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Falling from the Incomparable Gardens in Superior Saturday, Arthur, having won the Sixth Key, escapes impalement on Saturday's Tower by entering the Improbable Stair. His uncontrollable falling leads the Stair to spit him out somewhere completely unexpected - he is under attack from sentient plants in the Secondary Realms, and is unable to concentrate to use the Fifth Key to escape.

Meanwhile, Suzy Turquoise Blue, Arthur's friend, plots to escape from her prison in Saturday's Tower while battle rages above and below her. Saturday's forces are pressing into the Incomparable Gardens, but are also engaged in a fierce struggle to keep the Piper and his army of Newniths at the bottom of the Upper House. Suzy is being held by the intelligent but forgetful Sorcerous Supernumerary (meaning he failed his final sorcery exams), Giac. She, with some help from the sixth part of the Will, persuades Giac to free her and accompany her to the Citadel in the Incomparable Gardens.

On Earth, Leaf, responsible for the Sleepers from Lady Friday, struggles to cope with the aftermath of a nuclear strike and desperately needs help, especially since she herself has become a target for intruders from the House, namely Lord Sunday's Dusk and his 'pet'. Within the House, Nothing continues to rise and must be stopped before it can destroy the entire House and Universe.[3] Sunday intends to hold Arthur to ransom by controlling Leaf and his mother; to this end, he dispatches the "Reaper" (Sunday's Dusk) to take Leaf through the Front Door. It is then revealed that the Door is filled with Nithlings (and is, indeed, collapsing through contamination by Nothing). The Lieutenant-Keeper of the Door is vanquished in battle with them; the Reaper comes to his aid a few minutes too late, and the Keeper dies (handing over the post to an unwilling Leaf). Leaf, being the new Lieutenant-Keeper, cannot be compelled to leave the Front Door, so the Reaper goes back to Lord Sunday to report his failure.

Arthur returns from the unknown planet in the Secondary Realms by a supreme effort of will and control over the Improbable Stair; he believes he has returned to his bedroom on Earth, but as he searches his house he finds his mother (who went missing during the events of "Lady Friday") in the living room. As he approaches her he realizes that she can't see him. It is later revealed that Arthur's mother is trapped in a time loop and is being displayed as an exhibit in the Incomparable Gardens. He cannot interact with her; when he looks out of the windows he can see nothing but green leaves draped against them. Soon after, a Piper's child (employed as a gardener) enters the house with a flaming pitchfork; Arthur grabs and deactivates it, and forces the boy to lead him out of the house. The boy professes not to have heard of the upheavals among the Trustees; he thinks Arthur is the Reaper (leading Arthur to suspect that the Reaper is Sunday’s Dawn, Noon or Dusk).

As they leave Arthur's house, they are ambushed by Sunday's Dawn and Noon; and the Piper's child reveals himself to be Lord Sunday in disguise. After chaining him up by his arms to a colossal dragonfly, (the form of transport commonly used in the Gardens) they fly him over the Gardens to a smaller replica of the clock face that the Old One is bound to. Arthur, his Keys overcome by the superior power of the Seventh Key, tries to escape by using his own innate powers to form something out of Nothing; he fails to create anything, but he brings his childhood toy, Elephant, to life. He sets it to search for his confiscated Keys; meanwhile, he calls the Mariner to come and rescue him. Hours later, the Keys are sent to him and Arthur is able to free himself.

Leaf has ventured to the Middle House via portal and has joined forces with Suzy's band of motley Raiders in an attempt to infiltrate the Upper House, in order to prepare elevators for the Army of the Architect to get through to the Gardens. Fred Initial Numbers Gold, during an attack by the Piper's army, accidentally picks up Leaf's sword, and with it the post of Lieutenant-Keeper of the Front Door.

Arthur battles with Lord Sunday, who also has to contend with an invasion by the combined forces of the Piper and the subservient Saturday. The battle is taken to the Elysium, the epicentre of creation; it is here that the seventh part of the Will (a withered apple tree) is kept in a gilt cage. The Mariner opens it at Arthur's behest, but is killed in the process. The freed Will traps Sunday while Arthur claims the Seventh Key (in the form of a small key). When Dame Primus bites into an apple from the manifestation of Part Seven of the Will, the Will is made whole; Arthur unknowingly becomes its channel for its intended purpose - the destruction of the House. The Old One is freed, and He steps into the Will; it is explained that the Architect split Herself in two at the beginning of Creation to speed the evolutionary process, and the Old One is in fact a part of Her (but he had to be chained up when his views grew distinct from Hers), and the manifestation of the Will is the Architect in Her entirety. She reveals that, bored with life, She wished to return to Nothing, to see what it was like to die. She could not do so, however, without destroying the House, because in her anger She had chained the Old One to the fate of the House, and the Old One was anchoring her to existence. The Architect destroys the remnants of Creation with the powers of the Keys. Arthur, now omnipotent, survives and is anointed "New Architect" by the fading thoughts of the Architect. This is why She needed a mortal Heir, to provide a creative spirit to renew the Universe. Arthur decides to remake the Universe exactly as it was, using the Compleat Atlas of the House to provide the template. Because the Atlas holds a record of the House and Realms a few seconds before the destruction, Arthur is unable to save his mother, but he does split himself into the New Architect and the human Arthur, before his transformation into a denizen of the house. The new Arthur is not quite the same, being immune to all disease and with all the knowledge he acquired on his journey. He sends Arthur and Leaf back to Earth, by recreating the Seven Dials.

In the new Creation of the Universe, Suzy reveals her desire to be the new Lady Sunday, and pressures the New Architect to remake the House. The New Architect reveals he will soon bring back Doctor Scamandros, Fred, and Giac, the sorcerer, who could all help with the creation of new Denizens.