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This article is about the virtual world of Project Alicization and all non-system determined events in it. For information about the mechanics of the world, please see Project Alicization. You may also be looking for the anime episode with the same name.
Dark Territory and Taboo Index redirect here. You may be looking for the anime episodes with the same name: "Dark Territory" episode or "Taboo Index" episode.

The Underworld (アンダーワールド, Andāwārudo?) is the mysterious virtual world in which the Alicization Arc takes place.


With the era of the Cold War and, later, the collapse of the Soviet Union, people have been becoming less and less tolerant of the death of soldiers, while countries with large militaries, especially America, have been unable to give up their army munitions industry. With such conditions, the need for unmanned weapons to fight in wars instead of humans has arisen. However, as no countries export weapons to Japan, Japan's defense technology has become too weak and, eventually, Japan had to buy new equipment from America. Although, formally, America is supposed to work together with Japan on developing new technology, but in reality, Japan has only been given outdated equipment. Thus, the need for Japan to develop its own technology came.[1] Project Alicization, a top-secret government project run by Rath, a company affiliated with the Japan Self Defense Force (JSDF), was started to create the first highly adaptive, «Bottom-up AI». By using a 4th generation FullDive machine, called the Soul Translator (STL), Rath succeeded in copying the Fluctlights (souls) of twelve newborn babies, creating a «Soul Archetype», a non-developed Artificial Fluctlight that could be copied to create new Artificial Fluctlights, which would then need to be nurtured to mature into an individual. For this reason, a virtual world, codenamed «Underworld», was created using the free kernel version of the Cardinal System, The Seed, and then transferred into the STL mainframe via the Mnemonic Visuals feature of the STL.

Underworld is set in a past era, when science and philosophy were just being discovered, but instead of recreating a past era, limited terrain and certain customs were introduced so that the inhabitants of the world would form their own society.



The people of Underworld recognize at least five gods:

  • The Goddess of Creation Stacia (創世の神ステイシア, Sōsei no Kami Suteishia?) - the main goddess of the Human Empire, as well as the goddess of life and creation. According to the legends, she governs the existence of all animate and inanimate objects in the form of Life, displayed in the Stacia Window, and summons those whose Life expires to her side.[2] Marriages in the Human Empire are pledged to Stacia, who blesses the couple and allows them to have children.[3]
  • The Sun Goddess Solus (陽神ソルス, Hi Shin Sorusu?, derived from Latin "Sol" - "Sun") - the goddess of Underworld's star, Solus, that provides blessings to the world in the form of sunrays that increase the surrounding Sacred Power.[4][citation needed] Her blessings diminish during the night when the Solus sets.
  • The Land Goddess Terraria (地神テラリア, Chijin Teraria?, derived from Latin "Terra" - Earth) - the goddess of the earth that provides blessings to plants[citation needed] and protects metalworkers and craftsmen.[5] Provides Sacred Power through the earth, though this source of power is very limited in cities[6] and above the ground.[citation needed]
  • The Darkness God Vecta (闇神ベクタ, Yami Shin Bekuta?) - the ruler of the Dark Territory and the only god worshiped there. Vecta is said to love pulling pranks on humans, in the form of diseases[citation needed] or kidnapping people and stealing their memory.[7] Vecta was also the originator of the Dark Arts.[8]
  • The Goddess of the Moon Lunaria (月の神ルナリア, Tsuki no Kami Runaria?, derived from Latin "Luna" - moon) - the goddess of the moon who controls the dreams of Underworld's residents.[9]

World Creation[]

According to the story told by the Axiom Church, the world was created by the three goddesses, Stacia, Solus and Terraria,[10] but was then split by Stacia and Vecta into the Human Empire, overseen by Stacia, and the Dark Territory, ruled by Vecta,[3] after Solus drove away Vecta to the land of darkness with her holy spiritual light during the world's creation.[10] Ever since that time, the light of Solus has never shone on the lands of the Dark Territory.[7]

The Great War[]

In one legend, it is said that once every one thousand years, when the light of Solus weakens, the forces of darkness led by the dark knights would cross the mountain range will invade the Human Empire from the North Cave, West Gorge, South Corridor and East Gate. In that great war, the guards in the villages, the sentinels from all towns and the imperial army would form the Human Empire Army that would be led by the Integrity Knights to fight against the hordes of monsters, while nobles would support the Integrity Knights as the commanders of that army. Until then, the nobles are to polish their swordsmanship in preparation for the battle.[7][11]

The Truth[]

In reality, the existence of the five gods was forged by the Axiom Church to secure its authority over the Human Empire. Although none of the gods truly exist in the world, they are registered as super accounts in the system, though they had never been used since the creation of Underworld.[3][12]


Human Empire[]

The Original Four[]

The population of the Human Empire began around 70 Before HEC with two families of eight Artificial Fluctlights each in a small village at the center of the Human Empire, the village of Centoria. Both of these families had two real Rath employees nurturing them, while the rest of the villagers were simulated with placeholder NPCs. The four members of Rath raised the first sixteen Artificial Fluctlights to adulthood, teaching them everything from reading and writing to cultivation of crops and rearing of livestock to the morality of good and evil, however, one of the four employees lacked ethics and unintentionally corrupted one or two of the children by passing down his egoism and desire for wealth and dominance to them. After the Artificial Fluctlights reached the age of eighteen and started families of their own, the four humans logged out one after another by simulating an "epidemic".

The Growth of the World[]

After the «original four» logged out, the population of Underworld continued to grow, with the humans marrying when they were about twenty years old and bearing an average of five children, thus the 5th generation already consisted of 600 children, with about 400 still alive from the older generations. The children corrupted by the egoistic Rath employee became the ancestors of the future nobles as they secured their place as elites in the world. By the time of the 5th generation, the inhabitants of the Human Empire were already ruled by several lords, who, inheriting the egoism from their ancestors, earnestly continued expanding the land they owned, thus depriving the descendants of the non-corrupted first humans of land for cultivation. Most of the youth was then forced to work for the lords as tenant farmers, while some of them, who were not content with their social positions, set off from Centoria and traveled to the remote regions where they founded new towns and villages, like Zakkaria and Rulid Village, and thus acquired new land to cultivate.

Meanwhile, the lords that ruled over the capital held enmity towards each other, so there was a long period of time without any marriages between them. However, after some time, a political marriage happened between two families of lords for the first time. As a result of this marriage, a single daughter, possessing a higher level of egoism than any other lord in the world at the time, was born.

Axiom Church[]

The Axiom Church was founded around 30HEC (100 years after the creation of Underworld). At the time, the founder and head of the church was a girl named Quinella. Her Sacred Task was one not seen before in Underworld: "Sacred Arts Research". She soon became very proficient at the Sacred Arts and had discovered many new rituals that people could use in every day life. At the age of thirteen, Quinella decided she didn't want to rule over the people as a lord or baron - she wanted to have absolute control, she wanted to become God. To do this, Quinella started doing "miracles" in front of people, predicting storms and healing sick and injured people in the name of "god". She told the people that a shrine to worship god needed to be built in order to perform even greater miracles, hence a large marble spire was erected in the center of town. This was the beginning of the Axiom Church.[3]

Years later when Quinella felt her life was coming to an end, she desperately tried to find a form of Sacred Arts that could manipulate her «Life». Even at the verge of death, she still tried chanting various combinations of verses in the hopes of finding something that could help her. One fateful night, when she was just on the brink of death, Quinella discovered the Sacred Art: “Inspect Entire Command list”, and at the bottom of this list was the command that Quinella had been searching for, the one that would let her truly become God.[3] This command that she had found was one that took the administrator powers from Cardinal and transferred them to Quinella, allowing her to then use all the controls that administrators had access to, including the manipulation of «Life». Even after this act, Quinella's thirst for power was not satisfied and so she tried to eliminate the one thing that held equal authority to her, the Cardinal System, but accidentally ended up infusing it with her Fluclight. By doing this, she became less human and adopted the primary purpose of the Cardinal System: to preserve the Human Empire exactly as it was.[12]

Quinella then created the Immortal Walls in Centoria which divided the Human Empire into four. This was to create a physical barrier between the people and to make sure that the Axiom Church would have complete control of the relaying of information. She made it so that the people would remain reliant on the church and thus they would stay devoted to its preachings. Large physical barriers including: a huge, unbreakable rock; a swamp that could never be filled; a rapid, uncrossable stream and a gigantic unfellable tree were then put in the world to make sure that humanity could not expand past its current boundaries, effectively stopping all progress in the Human Empire. She also set down rules for the people, including the Taboo Index, and made sure every resident knew them so that no one could possibly oppose her. While this was all happening, the tower of Axiom Church was growing ever higher.[12]

Seventy years after Quinella assumed her position as administrator, she discovered that the capacity in her brain for storing memories was reaching its limit. In an attempt to stop this, Quinella attempted to transfer her memories into a young girl. However, this backfired as a Fluctlight could not bear the fact that there was an exact copy of it. But, instead of both of Quinella's Fluctlights breaking down, the young girl's Fluctlight collapsed a moment sooner and allowed the Cardinal System's error correction program to take control of her body, creating Cardinal. As both Cardinal and Quinella now deemed each other as different beings, their Fluctlight breakdown halted. Cardinal reacted a mere moment sooner and attacked Quinella first. However, Cardinal was eventually overpowered and forced to flee and seek refuge inside the Great Library Room. Afterwards, Quinella started avoiding death by deleting her most recent memories and spending most of her day sleeping on the top floor of the church to avoid filling up her memory capacity. She also started using the Synthesis Ritual on especially strong swordsmen and law breakers to turn them into Integrity Knights, who would fight the monsters of the Dark Territory, keep order among the people and defend her from Cardinal, whom she knew would be back one day to kill her. Cardinal would also try to seek help from humans in her quest to kill Quinella, but every time she found someone that might be able to help, Quinella was able to get to that person first.[12]

Through the Integrity Knights, the Church was able to maintain its rule over the Human Empire for another 200 years. However, the Church's rule became endangered when the «Load Test Stage» began to approach. Even with the great fighting prowess of Integrity Knights they would eventually be overpowered by the sheer numbers of the Dark Territory's forces, even if Quinella herself would join the battle. Knowing this would one day happen, the Axiom Church invented a story that on a day when the light of Solus would weaken, the forces of the Dark Territory would invade the Human Empire. Quinella used this story as a pretext for the foundation of the Sword Mastery Academy.[citation needed]

Dark Territory[]

In contrast to the Human Empire, far less is known about the history of the Dark Territory. There was once a time known as the «Age of Blood and Iron»[Japanese equivalent needed], where the different races that inhabited it constantly fought one another. This period came to an end following one final battle, which was so devastating that no living thing other than a lone black lily survived. Afterwards, the races signed a peace treaty and divided the lands of the Dark Territory between themselves. However, there were power plays involved in the treaty, such as in the case of the Goblins, who were given barren plains derived of resources. There were also some who believed the current peace was only a temporary truce to defeat their common enemy, the Human Empire, and that the fighting would begin once more once that goal was reached.[citation needed]


Human Empire[]

The Human Empire (ヒューマン・エンパイア(人界), Jinkai/Hyuman Empaia?) is where the humans live in the Underworld. It's a perfect circle with a diameter that measures around 1500 kilometers. The Human Empire is bordered by the Mountain Range at the Edge and connects to the «Dark Territory» via the «North Cave», «East Gate», «South Corridor» and «West Gorge».

The Human Empire is divided into four empires: Norlangarth North Empire, Eastabarieth Empire, Wesdarath Empire, and Southacroith Empire. The capital of all four empires is is their respective side of Centoria, from which the Human Empire is ruled by the Axiom Church and the four empires. Each empire is separated by the large «Immortal Wall» (不屈の壁, Fukutsu no Kabe?), which extends from the four corners of the Axiom Church and stretches to the Mountain Range at the Edge, thus limiting movement between the empires. An identification handprint is required to cross the Immortal Wall.[6]

About 80,000 people live within the Human Empire,[1] about 20,000 of which live within Centoria.[6] The four empires together have about 2,000 soldiers.

Norlangarth North Empire[]

Norlangarth North Empire (ノーランガルス北帝国, Nōrangarusu Kita Teikoku?) is the northern empire of the Human Empire. The empire has fertile grasslands, deep forests and many lakes. Rulid Village is the northernmost village in this empire. Zakkaria is a town to the south of Rulid Village. Deusolbert Synthesis Seven used to be the Integrity Knight overseeing the Norlangarth Empire.

Eastabarieth Empire[]

Eastabarieth Empire (イスタバリエス帝国, Isutabariesu Teikoku?) is the eastern empire of the Human Empire. A defining feature of a resident of the empire is black hair.

Wesdarath Empire[]

Wesdarath Empire (ウェスダラス帝国, Uesudarasu Teikoku?) is the western empire of the Human Empire.

Southacroith Empire[]

Southacroith Empire (サザークロイス帝国, Sazākuroisu Teikoku?) is the southern empire of the Human Empire. The Empire occupies an area that consists mostly of deserts.[13]

Other Places[]

Edge of Human Empire[]

Edge of Human Empire (人界世界の果て, Jinkai Sekai no Hate?) is the border between the Human Empire and the Dark Territory.

Mountain range at the Edge[]

The Mountain range at the Edge (果ての山脈, Hate no Sanmyaku?) is the mountain range that surrounds the Human Empire.

Dark Territory[]

The Dark Territory (ダークテリトリー, Dāku Teritorī?) is the country of demons, such as goblins and orcs. It is situated at the other end of the Mountain Range at the Edge. The population of the Dark Territory is approximately half the size of the Human Empire.[12]

Law System[]

All residents of Underworld are generally compliant to any law or rule that they regard as having authority, due to the effects of the Seal of the Right Eye. However, certain individuals, especially nobles, are able to circumvent the restrictions of the laws to satisfy their personal desires.

Human Empire[]

In the first decades of the Human Empire, the law system was passed down verbally from generation to generation in the form of parents teaching their children the basic moral rules that they should follow. Only after Quinella founded the Axiom Church, the first written law, the Taboo Index, was published.

Taboo Index[]

The Taboo Index (禁忌目録, Kinki Mokuroku?) is the absolute law in the Human Empire that was created by the Axiom Church to ensure Quinella's all-encompassing rule as well as to bind the masses with a sense of moral that suited the church's convenience. This rule system covers all crimes and their respective punishments, as well as prohibits actions that bring harm to other humans and limits hunting and storing food, as the world has limited resources.


Quinella became uneasy that there was a chance that people in the remote regions who have lost their parents before receiving guidance on ethics from them might discover the secret behind the increase in System Control Authority and, if they possessed the genes of nobles, they might follow their desires to such an extent that, by murdering people around them, they would soon over-rank Quinella in System Control Authority. Thus, to reduce the possibility of that happening to the minimum, Quinella published the first edition of the Taboo Index and ensured that every town and village in the Human Empire would get a copy. All parents were then tasked to teach the children in the settlements to abide by her law as soon as they learned language.

Over time, Quinella revised the Taboo Index, adding new clauses that helped people with everyday life by restricting access to swamps that were the source of endemic diseases, listing plants that negatively affect livestock etc., in other words, anyone who followed the Taboo Index would not experience any problems and thus removing the need for people to think for themselves and to question the rule of the Axiom Church.

Known Clauses[]
  1. 1st chapter, 1st passage, 1st paragraph: Loyalty to the Axiom Church.
  2. 2nd clause: Unless another clause applies, one shall not intentionally reduce the Life of another person.
  3. One may not claim items that belong to others without permission. This clause only applies to stealing from humans.
  4. All children must be taught the clauses of the Taboo Index.
  5. 1st chapter, 3rd passage, 11th paragraph: Not anyone is to go beyond the Mountain range enclosing the edge of Human Empire.
  6. One cannot kiss another person's lips (likely unless they are married).
  7. One may not enter swamps that are deemed to be the source of diseases.
  8. One may not hunt more animals than permitted.
  9. One must not abandon their Sacred Task during work days.
  10. One may not take up too many tasks.
  11. One can only hunt animals if they have the Sacred Task of "Hunter".
  12. Deliberately destroying items that are sold in the shop is against the Taboo Index.
  13. It's against the Taboo Index to not pay for an item if it was broken accidentally.
  14. If the owner excuses a person for accidentally breaking an item, it would not be breaking the Taboo Index.
  15. One may not run away after committing a crime.
  16. Deliberately destroying goods that belong to others is against the Taboo Index.
  17. Obstructing the nobles' right to judge is not allowed.

Other Laws[]

Aside from the Taboo Index, all empires have an «Empire Fundamental Law» (帝国基本法, Teikoku Kihon Hō?). As all crimes and punishments are covered by the Taboo Index, the empire law is largely made up of conventions concerning the masses’ class system, in other words, the rights of the nobles and the rights of the commoners. The law guarantees the 4th class and higher nobles the right to judge commoners in their territory and lower ranked nobles, usually by cutting down their wages, though younger nobles tend to resort to physical punishment as well. This law was likely established by Quinella when she appointed the lords of the land as nobles in the name of god to secure their support.

Each village also has its own set of rules, for example, Rulid Village’s standards, and certain institutions, like the Sword Mastery Academy, also have their own regulations which hold as much power as the higher laws, however, in case of conflict, the higher laws take priority.

Dark Territory[]

There are virtually no known laws in the Dark Territory, though generally one rule is followed above all else: the weak shall follow the strong.[14] As such, if one's leader is to perish, the one to succeed him would be the next strongest, under him. This is shown when the Leader of a group of Goblins was killed by Kirito, and immediately after, one of his subordinates stepped up to take his place.[15]


Human Empire[]

Feudal System[]

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Sacred Tasks[]

A Sacred Task (天職, Tenshoku?, literally "Vocation") is a lifelong occupation assigned to each individual in the Human Empire. Most people are assigned their Sacred Task at the age of ten during Spring, with very few exceptions, for example, the children at the Axiom Church who can receive their Sacred Task even at the age of five while a child who is very gifted in Sacred Arts may have their Sacred Task postponed to allow them to train their talent. A Sacred Task is usually assigned by a village chief, the ruler of a town, a high-ranking noble with their own territory or a minister from the Axiom Church - the people in charge of the area where the child was born.

The Sacred Task assigned to a person the first time cannot be chosen by the people themselves and, once a Task is assigned, it is impossible for even those who assign the Tasks to revoke them. However, certain tasks can be changed if the person is promoted, for example, a village guard may become a sentry in a local town, a student at the Sword Mastery Academy, and even an Integrity Knight in the end, if they meet certain requirements. Additionally, if a Task has an end and is completed, the person may choose their next Sacred Task themselves.

In practice, the eldest son of each household is usually given the same Sacred Task as their father: a tool shop's owner's son would continue working in the shop, a guard's eldest son would become a guard and a village chief's eldest son would succeed them as the next village chief. For farmer households, this standard usually applies to their daughter, second and third sons as well, though there are exceptions. People who are assigned Sacred Tasks that do not provide a source of income are given a wage from the village's or city's vault.

Once a Sacred Task is assigned, a person is only allowed to rest from their job on rest days and may not travel in a way that would prevent them from working on their Sacred Task, meaning that mostly only traders could travel long distances, if it is part of their Sacred Task, while an average villager would only be able to travel if it was possible to return to their Sacred Task by the next workday.

Certain Sacred Tasks also have certain benefits, for example, a person who is assigned to be a guard is assigned a real sword to use and may spend time practising their sword skills. Although it is possible for someone to help others with their Sacred Task, it's against the Taboo Index to "have many Sacred Tasks".


The original four inhabitants of Underworld, who were four Rath employees, named the first children using random syllables in katakana. Following that, several generations named their children after variations of their own name. However, after some time, a standard naming convention, in which every katakana used to produce a name symbolized a "wish" that the parents had for their child, arose within the Human Empire and most of the Dark Territory. Repetitions of certain sounds in a name often meant a greater desire for that trait, such as in the case of Rirupirin (リルピリン?), where R sounds, signifying "beauty", appear three times.

Sound Meaning Sound Meaning
Vowels Sincerity G Bravery
J Hardworking K Zeal
N Benevolence R Beauty
S Wit T Vitality
Y Gentle Z Talented at Military Arts

Although this tradition is widespread in the Dark Territory, certain groups have unique naming traditions. For example, goblins often use conjunctive forms of verbs, like Kosogi from the Japanese verb "to scrape". Additionally, distinguished families of the Dark Arts Users choose to name their children using only initials from ancient Darkness Script (English), such as D.I.L..

When it comes to writing names, the common folk of Underworld[citation needed] often use katakana. However priests are able to transcribe kana names into the alphabets of the Holy Language. Rather than a direct transliteration, the process instead involves anglicizing the names[16]. Thus, ユージオ becomes Eugeo, instead of Yujio.


There are two known languages within Underworld: the Common Tongue and the Sacred Tongue.

Common Tongue[]

The Common Tongue (汎用語(はんようご), Han'yō-go?, literally, "General purpose language") is the main language used for writing and speaking in Underworld. It is the equivalent of the Japanese language in the real world, though the language is supplemented with a few words borrowed from other foreign languages. However, the major difference from its counterpart in the real world is that only about 1000 kanji, about the equivalent of 30% of JIS Level 1, are used in Underworld, while other words and most names are written in kana. Although the same language is used throughout the Human Empire, several accents do exist.

Sacred Tongue[]

The Sacred Tongue (神聖語, Shinsei-go?) is the name given to the English language, though supplemented with a few words from other languages, by the residents of Underworld. This language is regarded as a sacred language used to ask the gods for miracles and is not considered as having any special meaning by the average resident, except for those who study the language for Sacred Arts. The language is mostly used in chanting the verses for Sacred Arts and written in system windows, like the Stacia Window, though a few names are also derived from this language, for example, the Gigas Cedar or the Dark Territory. The language can either be written in the English alphabet or in katakana for easier reading.

According to legends spread by the Axiom Church, the Sacred Tongue was passed down to the Administrator by the three goddess during the creation of the world. As the Axiom Church restricted the knowledge on the meaning behind the vocabulary of the Sacred Tongue to just those used in Sacred Art rituals, no known dictionary for the language exists outside the Central Cathedral.[17]


For a list of events in Underworld, see Underworld Timeline.

The humans in Underworld have their own calendar, called the Human Empire Calendar (人界暦, Jinkai-reki?, abbreviated as HEC), which was developed by the Axiom Church. This calendar starts dating from about seventy years after Underworld was created, as the Axiom Church attempts to maintain the falsified history that it spread throughout the Human Empire. As the time flow in Underworld depends on the Fluctlight Acceleration rate set, the HEC cannot be aligned with the time in the real world.

Like its Japanese equivalent, the HEC has twelve months per year and, like the Japanese calendar, the names of the months are derived from the number of the month, for example, the equivalent of January is the 1st Month (一月, Ichigatsu?), the equivalent of February is the 2nd Month (二月, Nigatsu?) and so on.


  • Although the order of most names in the series use the Japanese order of the person's Last name then First name, as the setting of Underworld seems be the Middle Ages of Europe, the names of Underworld residents use the Western order of First name then Last name.
  • Only nobles and rich and/or famous non-nobles have the right to have a family name in Underworld.
  • The metric system is used in Underworld, however the names for the units slightly differ from those in the English language, even though they have the same value. E.g. meters are called mer (メル, Meru?), kilometers are called kilor (キロル, Kiroru?), centimeters - cen (セン, Sen?), millimeters - mil (ミル, Miru?), liters - lil (リル, Riru?) etc.
  • Shia is used as a currency of Underworld.
  • The map of Underworld imitates Rath's logo: the Human Empire and the Obsidia castle are like the big and small gears, while the shape of the world and the shape of the logo are like the nose of a pig.[18]



Underworld Locations Navigation Bar
Centoria Central Cathedral - Great Library Room - Sword Mastery Academy
Norlangarth North Empire Gigas Cedar - Rulid Village - Sword Mastery Academy - Zakkaria
Mountain range at the Edge North Cave - East Gate - South Corridor - West Gorge