The Will is the document left behind by The Architect, dictating what was to happen in the House. Instead of complying with the will, the Morrow Days broke it up into seven pieces, each hiding a different piece. Eventually, Part One of the Will escaped and began to look for a suitable heir, intent on guiding him to his destiny. During the series, the Will takes the form of Dame Primus. During Superior Saturday , the Will splits into two bodies, Dame Quarto and Dame Septum, in order to help hold back the tide of Nothing.
The First Part: The Frog
The First Part of the Will (paragraphs three to seven) was hidden by Mister Monday in a crystal, which was in turn encased in a box of unbreakable glass. This was then covered with a cage of malachite. The whole box was put on the surface of a dead sun at the end of Time, guarded by twelve metal, sword-armed Guards known as Sentinels. Monday's Dusk indirectly, but intentionally, freed the Will.
The Will then took control of Mister Monday's butler, Sneezer, and persuaded the sloth-afflicted Monday to give up the Minute Hand half of his Key to Arthur Penhaligon, a mortal. Sneezer convinced him that the Will would leave him alone if he relinquished his Key to a Rightful Heir. However, their plan hinged on the fact that the Heir would soon die, as Arthur would indeed have done but for being in possession of the Key. The Will left Sneezer, and took the form of a jade-coloured frog and leapt inside the throat of Suzy, forcing her to help Arthur in the Lower House and defeat Monday. The Frog then took the name and form of "Dame Primus", a tall, attractive, and imposing figure who became Steward of the Lower House and the First Key when Arthur returned to Earth. She is often exclusively focused on fixing the much-decayed bureaucratic situations within the House, even when Arthur wishes to do otherwise. With the addition of other Parts of the Will, Dame Primus grows taller, stronger and more knowledgeable, and her severe beauty becomes more apparent. The Frog embodies either Fortitude or Diligence as one of the Seven Heavenly Virtues being the opposite of the Seven Deadly Sins.
The Second Part of the Will: The Bear
The Second Part of the Will (paragraphs eight to thirteen), also known as "Claws", was hidden by Grim Tuesday within a worldlet in the heart of a sun in the Secondary Realms, in the form of a Sun Bear. The Mariner was charged with guarding it, but, as he is resentful of Tuesday's control over him, he helped Arthur rescue it. Unlike the First Part of the Will, the Bear would not recognize Arthur's claim until he was notified by Dame Primus. Instead, the bear ordered a contest of creation, using the Second Key, which were the gauntlets worn by Tuesday. Arthur won, and after he fixed a breach into the Void of Nothing, the Second Part of the Will merged with the First. Its virtue is either Prudence or Patience.
The Third Part of the Will: The Carp
Known as the Carp, the Third Part of the Will was hidden within a worldlet commanded by Feverfew, hidden in Drowned Wednesday's stomach. Wednesday wished to execute her clause of the Will, but was stopped when Superior Saturday betrayed her. The Trustees (save Monday, who was afflicted with sloth) took Wednesday's portion of the Will and gave it to Feverfew to hide, additionally limiting Wednesday's use of the Key to keeping the shape of the enormous Leviathan she was to become.
Several of Feverfew's escaped slaves hid in a cave on a remote side of Feverfew's island with the Will, in the form of a carp. The Carp proclaimed itself a god, and has accumulated a cult following. The Carp is always preaching about the values of Faith, the virtue it embodies. Arthur was able to free the Third Part of the Will with the aid of Leaf and Suzy. The Carp is in fact a fish.
The Fourth Part of the Will: The Snake
This part of the Will takes the form of a snake wrapped around the sword that is the Fourth Key, wielded by Sir Thursday. The Fourth Part of the Will is able to free itself, but first Sir Thursday must be distracted sufficiently; this was accomplished by invoking his wrath. After being freed, it is obsessed with bringing Thursday to justice, and is barely subdued by Arthur. When Arthur goes to meet the Piper, the Fourth Part of the Will joins him, and contrary to Arthur's wishes, spits corrosive acid into the Piper's mouth. The Will assures Arthur that as this acid was not "poison", it did not disobey his command to refrain from poisonously biting the Piper (being able to choose whether or not to be poisonous, and if so, to choose its type of poison). During Arthur's meeting with the Piper, the Piper notes that the Fourth Part of the Will speaks in a tone that is familiar to him. The Fourth Part of the Will embodies Justice or Chasity.
At the beginning of Lady Friday the Fourth Part of the Will has joined Dame Primus. Dame Primus thereafter begins to pay attention to justice and to exhibit snakelike features. She orders all the Piper's Children in demesnes ruled by Arthur to be killed, as the Piper is their enemy; Arthur quickly overturns this order. The appearance of her snakelike fangs and forked tongue, possibly provoked by a moment of passion, is the second instance of suspicious behavior displayed by Dame Primus (the first being refusing a call from Leaf, who was then trying to help Arthur).
The Fifth Part of the Will: The Beast
The Fifth Part of the Will appears as a large, half-reptile, half-bat monster or Wyvern, worshipped and feared by the Winged Servants of the Night. Arthur finds it imprisoned by Lady Friday in the "Inner Darkness" of the cave system the Winged Servants of the Night use as their eeyrie, on the
Top Shelf of the Middle House. Known to the Servants as the "Beast", the Fifth Part of the Will is a pleasant and agreeable creature, unlike the other parts. It mentions that the "Key" Friday left is not the real Key, but a trap, and that she has not legally abdicated her rule of the Middle House. After being released, the Will accompanies Arthur, Suzy, Fred, Banneret Ugham, and a host of Dawn's Gilded Youths to Lady Friday's Scriptorium, where Friday claimed to have left the Fifth Key.
There, they find that a battle between the Piper and Superior Saturday's forces has left Saturday's Dusk dead, and the Piper's Children unconscious. Despite Arthur's and the Will's warning of a possible trap, the Piper orders Ugham to take the fake Key from its pedestal, activating the trap and breaching the Void of Nothing. This kills Ugham and quickly consumes the Scriptorium and most of the Top Shelf. The Piper uses his Pipes to enter the Improbable Stair, in order to escape, while the Will manages to save Arthur and his allies with a sweep of its tail. The Will then tells Arthur to use the Keys to close the rift into the Void of Nothing; after summoning all four Keys to help him, he successfully closes the Void. Using the Keys, Arthur takes the Improbable Stair to Monday's Dayroom, where Sneezer sends them to Lady Friday's sanctuary in the Secondary Realms. There, with the aid of the Will, Arthur defeats Friday.
After defeating Lady Friday in her sanctuary, Arthur gives the first four Keys to the Fifth Part, to return them to Dame Primus. Before leaving, the Will apologizes for the behavior of the other Parts of the Will, speculating that Dame Primus will be easier to work with once it has joined her; this is later shown to be incorrect, as she acts even more rebellious than before. It represents the virtue of Temperance.
The Sixth Part of the Will: The Raven
The Sixth Part of the Will appears as a raven and is also capable of transforming into a variety of
other things. The Sixth Part of the Will was able to communicate with Arthur whenever he was drenched in rain, because Superior Saturday had hidden the Will in the rain by scattering its type in every raindrop, the most complicated method of hiding the Will seen so far. To free the Will, Arthur had to go to the Midtower Rain Booster Tank, because that was where the rainwater was collected. The Will then instructed Arthur to swim out to the middle of the Tank and call for the Will with his mind, so it could resume its form.
It likely represents the virtue of Charity, showing more kindness to others than the other parts of the Will, evident when it shows a willingness to save Suzy from the Artful Loungers. Suzy later expresses regret when it has been absorbed, saying "it was the best part, if you ask me," and hopes that it will have some effect on Dame Primus, but, like in the case of Part Five, this does not prove to be the case. It appears to be the most intelligent part of the Will, as it denies the rumours that if the House is destroyed, then the Secondary Realms are also destroyed. The Will instead says that the whole of creation will only cease to exist if the Incomparable Gardens are destroyed, as they came from the Void first and are the true epicenter of the Universe.
Interestingly, Part Six is the only part of the Will to have a main part outside of its respective book.
The Seventh Part of the Will: The Apple Tree
The Seventh part of the Will appears an apple tree. It is able to communicate with Arthur with restrictions and its capabilities to do so improve as Arthur gets closer. The Seventh Part of the Will is locked up in a cage, that the Will explains brings death to all that touch it and can only the Seventh Key or the Mariner's Harpoon can open (which subsequently kills the Mariner).
It represents either the Virtue of Hope or Humility. This is suspected because after The Apple Tree joins Dame Primus, Dame Primus becomes easier to work with because she needed humility for Part Five and Six to make an effect. It is likely a reference to the tree of knowledge in the Garden of Eden. It uses its roots and branches to snare Lord Sunday giving Arthur time to claim the Seventh Key.
The Complete Will of the Architect, Dame Primus
The Will is in fact the embodiment of a part of the Architect. The Architect wished to go beyond and leave the realms she had created, but in the beginning she had wrought the Old One from herself which chained her to this universe. She could not free the Old One from his bonds without first destroying all of her creations, so she made the Will.
When Dame Primus finally joined up with the Seventh Part of the Will, words written in flame appeared reading " Let the Will be done " and Arthur unknowingly uses the power of the keys to conjure a gout of nothing that destroyed the rest of the Incomparable Gardens, the Elysium. The Old One then appeared and became one with the Architect once more. She tells Arthur the true story of the creation of the Will and the House. She then lets herself return to Nothing, in a way similar going to sleep.
The Will was not so much made to choose an "heir" but a New Architect who would create a new universe.