Sword Art Online Light Novel Volume 12

The twelfth volume in the Sword Art Online Light novel series and the fourth installment of the Alicization arc.

Chapter 7 (The Two Supervisors, 5th Month of Human World Calendar 380)
Kirito recollects his life since he entered high school, and how he has been forced to leave his education three times already (one time because of the SAO incident, another time due to being stuck in Underworld and now again because of breaking the Taboo Index). He then resumes his talk with Cardinal  who continues the story of Quinella after she had found the list of system commands in Underworld.

She explains that when Quinella attempted to steal the system authority level from the Cardinal System using a complex system command, Quinella accidentally burned the primary instruction of the Cardinal System (to preserve regularity of the world) onto her Fluctlight as a non-changeable principle due to her low knowledge of the complex syntax of supervisor level commands. Because of this, Quinella inherited the Cardinal's duty of regulating the world, but pushed it to even greater extents - to regulate the residents as well.

It was Quinella who divided the human world into four empires and created different obstacles, such as the Gigas Cedar, to restrict the movement of the residents and thus be able to regulate them. Then Cardinal proceeds to explain the origin of Quinella's worry and how she created the Synthesis Ritual to exceed the limit of her memory, which is estimated to be about 150 years. The Synthesis Ritual allowed Quinella to manipulate the Fluctlight of a chosen person and thus she used this ritual to create a backup of her memories in another person's Fluctlight. At the time, a ten-year-old daughter of a furniture's shop owner had become a nun at the Axiom Church due to her above average System Control Authority. Due to her young age and thus, a large free memory capacity, the girl was invited to the top floor of the Cathedral, where Quinella attempted gaining control of the girl's Fluctlight and using it to store a back-up of Quinella's memories. The Synthesis Ritual was successful and Quinella's compressed memories were successfully copied onto the girl's Fluctlight. However, as Quinella and the girl regained consciousness at the same time after the ritual, they realized that they were exactly equal existences and began to break down due to the shock caused by this realization. The nun's Fluctlight was the first to break down and, at that moment, the Cardinal System's sub-program, which was copied onto the nun's Fluctlight along with Quinella's memories, managed to assume control of the young girl and the two Fluctlights stopped breaking down. Cardinal immediately attacked Quinella to gain the upper hand and, at first, she was winning because of taking the initiative. However, Quinella then realized a weakness that Cardinal had and made her room a place where no Sacred Arts could be used, generating a weapon afterwards. Although both generated weapons to fight, but Quinella had the advantage due to being used to her body, while Cardinal had yet to adapt from controlling a grownup's body to that of a young girl, so Cardinal had to escape. She took refugee in the Great Library Room, which Quinella had created to store her memories and had made hard to access from the outside, and destroyed its only connection to the Central Cathedral and thus preventing Quinella from being able to enter the Library.

She waited in the Library and released familiars to look around the Human World for people capable of helping her, but whenever she found someone, Quinella always reached the person first and captured him or her to turn into another Integrity Knight. During the over 200 years without any success, Cardinal began to grow impatient, until she heard rumors that the Gigas Cedar was cut down by two youngsters. She immediately sent Charlotte, her most trusted familiar that was stationed in the northern region, to find the two youngsters and investigate how they were able cut down the Cedar. Having deduced that Kirito was in fact a real human after a year's worth of observation, meaning that Kirito would be immune to Quinella's Fluctlight altering commands and would be able to face Quinella head on, Cardinal set up the maximum amount of backdoors in the Cathedral, to await for the time when Kirito would enter the Cathedral as either the winner of the Four Empires Unity Tournament, or as a criminal who broke the Taboo Index. As Kirito ended up breaking the Taboo Index, Cardinal guided the two youngsters via Charlotte to one of the backdoors in the Cathedral's garden, after they had escaped their prison.

Chapter 8 (Central Cathedral, 5th Month of Human World Calendar 380)
Volumen 12

(pardon my bad attempt at summary, this is my first wiki edit. Do help me out by editing this)

Quinella explains to Kirito while Eugeo is distracted what is happening and tells him her plan to save the world. She explains to Kirito how <> works. <> works by releasing all the memories of the weapon. For example, Eugeo weapon, <> is a eternal block of ice before it was a weapon. Thus, it retains the memories of being a ice. So, when Eugeo releases its memories, the sword reverts back to a block of ice, having all the attributes of a block of ice and a sword. All sacred class weapons have memories previously. In order to create a weapon of sacred class, one needs to give a item of equal value. She helps Kirito and Eugeo realise their swords memories and unlock their powers and special moves. She also gives Kirito and Eugeo two daggers made of her own hair, thus connected to her, as a secret weapon to beat the Admistrator. She then release them into the Center Catherdral for them to retrive their weapons.

After reentering into Center Catherdral, Kirito and Eugeo when to retrieve their weapons. After that, they got into a fight with Sythesis No.7, who uses a sacred instrument based of a phoniex. They beat the Intergrity Knight and banter a bit with him about Central Cathedral and the nature of its rule. Finally, they convinced the Intergrity Knight not to pursue them. Whether the Intergrity Knight will become their ally remains unknown.

They then meet into two children (whose pictures are shown on the cover page). They trick Kirito and Eugeo into lowering their guard, before poisoning both of them and bringing them to the 50th floor. In 50th floor, 5 Intergrity Knight awaits them. The two children hoped to use Kirito's and Eugeo's life to exchange for a the chance of becoming a true Intergrity Knight (the two children are in fact Intergrity Knight Synthesis No.28 and 29 but they still have not received their sacred weapons and armour) but Kirito escapes the poison and poisons them both using their own poison. He then battles the Intergrity Knights before emerging victorious, suffering serious injuries in the process.

Moving on, they progress to the 80th floor. There, they had a chance meeting with Alice, whom they have comed to rescue. Alice, having no memories of them, shows no mercy. Kirito challenges Alice to a sword fight without using their sword's special abillities in a bid to give Eugeo a chance to stick Quinella's dagger into Alice. Alice, possesing a overpowering sword (which she claims is the oldest and most ancient sacred weapon amongst them all, planted down by Rath as a indestructible object at the very begining of the world) easily beats Kirito, but Eugeo manages to pull off his swords special move and immobillise both of them. Alice, however, breaks the seal with ease. Kirito, seizing the oppurtunity, attacks with his special move. The special moves of Alice and Kirito clash, sending both of them tumbling out of the Center Catherdal, a few thousand mels off the ground. The wall broken by the special moves reseal itself and Eugeo tries to break it in an attempt to reach Alice and Kirito, before giving up in despair. The story ends at this point.