Shuna

Octagram: Created by Guy around two thousand years ago as part of his game against Rudra, he Demon Lord council is something of an international political organization not dissimilar to the Council of the West. It primarily consists of powerful individuals who rule over vast amounts of territory and are at the head of monster society.

The number of members and the name of the council has changed multiple times throughout history. Originally, there were only three members: Guy, the founder of the council and its indisputable leader throughout its various iterations, along with Milim Nava and Ramiris. Those three eventually came to be known as the Ancient Demon Lords.

Following the last Tenma war five hundred years prior to Rimuru's reincarnation, the maximum number of members was capped at ten and the name "Ten Great Demon Lords" was tentatively adopted based on its existing common use in human society. However, the organization was eventually restructured and the name "Octagram" was ratified as the council's proper name, while also further reducing the maximum members to eight.

Veldora Tempest: He was born as the incarnation of chaos, having control of wind, water and space. He was the fourth to emerge as a True Dragon among his siblings. From the moment of his birth, Veldora has been plagued by a relentless sense of restlessness, which often leads him to embark on destructive rampages often manifesting in violent storms. His boredom compels him to seek out challenges from his elder sisters, Velzard and Velgrynd, in order to assert his superiority. However, this cycle of reincarnation and rivalry has left an indelible mark on Veldora, instilling within him a perpetual fear of his formidable sisters that persists to this day.

One day about 2,000 years ago, Veldora went and trashed a vampire city ruled by Demon Lord Luminous Valentine to relieve his boredom, making him bear the grudges of the Queen of Nightmares since.

When the Eastern Empire dispatched an Army to expand their territories 300 years ago, they encountered Veldora in Jura Forest and got crushed. Because of that, a Hero was dispatched to defeat him. The Hero imprisoned him with her Infinity Prison as a result, sentencing him to live his days in monotonous boredom in the Sealed Cave.

Central World: Continents: Magic Continent: On the far west, there are the "Barren Lands", a great expanse of inhospitable sandy desert contaminated with magicule radiations where the ancient ruin of 'Soma' is located and the territory of Demon Lord Dagruel, on its border lies the Holy Empire of Lubelius, a rich land and the territory of Demon Lord Luminous Valentine as well as the home of the Western Holy Church.

In the center of the continent lies a great collection of countries collectively referred to as the 'Western Nations', as well as the Jura Forest which contains the Jura-Tempest Federation and is the abode of Veldora. Both are considered the territory of Demon Lord Rimuru, although he's only publicly the ruler of the Tempest Federation. There's also the 'Great Canaat Mountains' to the north, a great expanse of mountains ruled on the surface by the Dragon lords who reside in the 'Dragon Roost' at the peak of the tallest mountain, and ruled underground by the Armed Nation of Dwargon. And at the southern border of Jura Forest is the Sorcerous Dynasty of Sarion, a collection of 13 elven states that swear allegiance to their divine emperor Elmesia El Ru Sarion, but otherwise act independently to each other. Its "capital" is the state of Elmin where the emperor and her family reside.

Ice Continent: is the northern continent as well as the domain of the first Demon Lord, Guy Crimson. Its surface is constantly under a thick layer of permafrost and harsh weather due to Velzard's aura, making it inhospitable to all but the strongest of living beings. The only known settlement is the Frost Palace, where Guy and Velzard, as well as a massive army of daemons under the leadership of Rain and Misery, call home.

El Dorado: s the southwest continent singlehandedly ruled by Demon Lord Leon Cromwell. It has a large and active supermassive volcano at its center that constantly spews out ash and draws out large mineral deposits from deep under the surface, including gold, the source of El Dorado's income. The capital of El Dorado which resides besides a volcano, was also home to a "Hell Gate" managed by Jaune.

Holy Empire of Lubelius:

The nation is led by Holy Emperor Louis Valentin, who, secretly is a Vampire and subordinate of Demon Lord Luminous Valentine the "God" of Luminism, and the true ruler of Lubelius. Until his death, Roy Valentin, the twin brother of Louis, played the role of the "evil Demon Lord" Valentin to unite Lubelius against a supposed ever-present threat.

To gain military strength and raise morale amongst the populace, the nation founded the Temple Knights and Crusaders led by Hinata Sakaguchi. These knights were recognized as a powerful military force across the Central World.

Great Jura Forest: For a long time, the Great Jura Forest had served as a buffer zone, mitigating direct confrontation between countries. It's unknown whether the land started off barren or was already a forest, but it was inhabited by Storm Dragon Veldora and had been his territory for centuries. Under the influence of his magical energy, the forest expanded and grew to cover a vast amount of land.

Until Veldora's disappearance from the forest, the Demon Lords had a mutual pact in place that forbade them from stepping foot there, to prevent Veldora's seal from being undone. Due to the presence of the dragon, even in his sealed state, his presence alone was presumably enough to deter the Eastern Empire from invading. The monsters of the forest were under the impression that they received divine protection from the Storm Dragon - that was why they could live inside that brutal surge of magic power it emitted. Though it was unpleasant, it was because of his existence that external aggression was impossible.

After Rimuru's coronation as a Demon Lord and his induction into the Octagram, he was granted ownership of the entire Jura Forest. Some of the forest was leveled in establishing Tempest, and future developing cities and villages now required permission from Demon Lord Rimuru to access the forest's resources.

Jura-Tempest Federation: Initially founded near the Sealed Cave after abandoning an old goblin village, the nation started off as a new Goblin village built by dwarven craftsmen. This village then joined with the lizardmen, emancipated orcs (now High orcs), surrounding Goblins (now hobgoblins) as well as the dryads and treants to create The Jura Forest Alliance which, several months later, evolved into the Jura-Tempest Federation, kicking off the founding of the nation with a magical treaty with the Armed Nation of Dwargon.

The Monarch and active Head of State of the Jura-Tempest Federation is Demon Lord Rimuru.

Due to its geographically central location, sound military security, extensive infrastructure and road systems, Tempest is an economic hub where many nations trade or pass through while trading with other nations. As such, Rimuru City is home to a large variety of shops, species, cultures and infrastructure.

Tempest's chief exports are mainly high-quality manufactured good. Namely, the nation is well known for its large quantity of potent healing potions. Other exported goods include alcohol in the form of Brandy, Wine and Whiskey; silk among other fine fabric clothing, and top-tier dwarven/ogre crafted weapons, armor, and accessories. Production of goods in Tempest is overseen by "Goblin Lord" Lilina.

Magicule: are a type of spiritual matter that is heavily influenced by the minds of living beings and is able to take on many different properties depending on the situation. They are both the building blocks of, and sustenance for, monsters.

Magicules are similiar to atoms and made up of Spiritrons. They are invisible to the naked human eye and despite having mass, do not normally interact with most types of physical matter and energy, although they are capable of doing so. They act as a sort of radiation and can be found inside of materials as well as in the atmosphere.

Magicules are a particle highly susceptible to the thoughts and emotions of living beings. At the most basic level, this can be utilized to fill magicules with one's intent and then flinging them at a target, achieving a sort of telepathic communication. More advanced practitioners can fill magicules with complex images of phenomena by imagining the laws behind them, changing the form of the magicules to match that of the mental image, and performing what is known as Aspectual magic.

Western Holy Church: refers to the authority of the most widespread religion in the Western Nations, i.e. Luminous Faith

The Church is influential because it sends out troops that exterminate rampaging monsters in such regions where the local rulers either do not possess any stakes or any interests in them, or simply got no standing army left to deal with it.

Principles The Church recognizes One God Luminous as their sole and absolute deity, not recognizing the existence of any other gods.

Their central dogma is that monsters are evil and should be exterminated, hence the existence of Temple Knights and Crusaders tasked with monster slaying. However, practitioners of other religions were not protected.

Otherworlder: is a term that refers to humans that come to the Central World from other worlds.

Summoned: are the most common type of otherworlder, brought over through summoning rituals. In the process of crossing worlds, the summoned is exposed to a large concentration of magicules dense enough to kill any normal human. Only those that bear a strong soul and mind can endure the strain of the journey.

From the massive energy taken in by the summoned, Unique skills and other special abilities are born as a response to their desires.

Stray: are otherworlders that arrive by sheer accident. There is no clear cause or pattern known for why this happens, but in general, it's considered a one-way street and the phenomenon is not known to happen in reverse.

Reincarnated: or Transmigrant, refers to individuals that arrive with no body and just their mind, being reborn as an inhabitant of the central world. Reincarnation tends to happen randomly. Although there are those among the reincarnated who still remember their past life, to have reincarnated from a different world is exceedingly rare. Moreover, one would normally be reincarnated as a human. For someone to be reincarnated as a monster, and from magical energy itself, was something that remained unheard of.