YGGDRASIL

YGGDRASIL (ユグドラシル Yugudorashiru) is a fictional online game in OVERLORD series. It is a DMMO-RPG (Dive Massively Multiplayer Online Role Playing Game) developed in Japan, serviced from 2126 AD to 2138 AD.

Introduction
YGGDRASIL needs an exclusive console to play, which records logs for a week. Though the game is a full virtual reality one, in accordance to physical laws, it does not provide a sense of taste and smell, and has a limited sense of touch. Due to the lack of such technology when the game was developed, facial expressions and artificial intelligence are not supported.

The most distinctive feature of YGGDRASIL is its flexible system. Players can select numerous races and jobs and various tools allowing for customization. If you used creator tools that were sold separately, you were able to alter appearances of weapons and armor, interior data, character visuals, and detailed settings of a player’s home. It seems that the customization system is really far-reaching, even extending to basic programming.

Also, the game had a system where players could even pay a fee in order to participate in a lottery to win a rare item.

However, YGGDRASIL was a game where information itself had value. Like the case with World Class items, the number of people who freely shared newly discovered information with others was small. This was especially the case with classes that had a secret weapon such as Eclipse.

In the game YGGDRASIL, there are endless discoveries (special classes, items, etc) which players can possibly find and obtain through adventures, focusing on certain skills like instant death spells, etc. Another example is the Caloric Stone being a World Item among one of the hidden items discovered in the game.

However, parties were made up of six people in total, and a raid could have a maximum of 5 parties only. The first time one ran a dungeon, there would be a bonus, or about 10% more treasure chests. Also, the first time a dungeon was cleared, the big treasure chest would offer equipment with item levels up to 10-20% higher than usual. Clearing the dungeon under certain conditions can even be awarding like being granted a World Item such as the Throne of Kings.

While so, there are also a little over 800 guilds created within the game, consisting a type of guild's ranking system among them all. In addition, discovering a dungeon could affect the world ranking of a guild. On the other hand, YGGDRASIL have a clan system which differs from a guild system although the latter has both.

Furthermore, there does exist other functions (Forced System Access, Chat, Call GM, Log Out, and so on) used in the game. An example of this function is the existence of a chat channel, where players can look to for finding recent news like the shutdown of YGGDRASIL.

World
As it can be guessed from the title, YGGDRASIL mainly refers to Norse mythology, and has nine separate worlds based on it: Asgard, Álfheimr, Vanaheimr, Niðavellir, Midgard, Jötunheimr, Niflheim, Helheim and Múspellsheimr. Each world is a leaf of Yggdrasil. Other leaves were eaten by Navagraha the World Eater, or shed and transformed into World Items.

Each of them was ridiculously huge, and there were many places within them which were difficult to explore. For instance, there were gigantic swamps, verdant expanses of rainforest, scorching deserts, and the like. One needed special equipment to delve into the dungeons there, as well as a proper strategy and the determination to throw one’s life away for the trip. This was because these hard-to-find dungeons contained monsters which dropped valuable data crystals.

To add on, some dungeons could only be found under certain conditions. For example, the entrance to a dungeon amidst a field of flowers in the depths of a forest could only be seen under the light of the full moon. Additionally, there was also the Frozen City in Niflheim, which could only be entered during a blizzard.

Level
In YGGDRASIL, the maximum level cap for a player can reach is 100. When a player character dies, it loses 5 levels and randomly drops one's equipment they had on. One could lose one or more pieces of equipment depending on how very difficult the dungeon expedition was. The developers designed the game so that the most valuable gear would be dropped first, which meant that the chances of an item which was key to the player’s strategy being dropped would greatly increased.

However, the death of a character with level lower than 5 will just revert the player back to level 1. This was not a big drawback, because experience points could be regained easily, unlike in other games. Even if one’s levels went down for a while, the loss could be quickly recovered.

Nevertheless, this penalty can be reduced by using certain revival skills or cash items. When a player revives by skill, it can select the location he or she desires.

Optionally, there were four different methods of resurrection to choose from in exchange for experience points. The first type was on-site resurrection. The second type was resurrection at the entrance of a dungeon. The third type was resurrecting at a nearby safe town. Finally, the fourth type was resurrection at a specified location, such as a guild. On the other hand, NPCs belonging to players or guilds can revive instantly by paying the right amount of gold and fee depending on its level.

Races
Races of YGGDRASIL can be roughly categorized into three taxa. There are more than 700 races, including racial class that needs certain level of low rank racial class to learn. Some items can change races permanently. In the game, humans and demi-humans, who had limited lifespan, would grow and age normally. In contrast to them, heteromorphic races with unlimited lifespan would stop growing after a certain stage.
 * Human Races include human, elves, dwarves, etc. Human races are weakest in basic status and cannot have racial level. Instead they can learn more classes which provides high status or powerful skills more easily, giving them high potential. Adding familiar appearance to these advantages, human races were most popular in YGGDRASIL.
 * Demi-Human Races include orcs, ogres, lizardmen, etc. Demi-Human races can get more basic status and have racial level. Demi-Human races are similar to the average between Human races and Heteromorphic races.
 * Heteromorphic Races include slimes, vampires, devils, etc. Heteromorphic races own most powerful basic status, which can be even more strengthened by increasing their racial level. High-rank races also provide special ability similar to that of monster's. Yet Heteromorphic races were very unpopular, as the racial level limits job level one can learn, and PK on Heteromorphic races doesn't give any penalty to the player who killed Heteromorphic race player.

Classes
More than 2,000 classes exist in YGGDRASIL. Basically, 15 is the highest level reachable in a single class, yet some high-rank classes seems to have lower level limits. Thus, a 100 level player owns at least 7 classes. If one ignores efficiency, it is also possible to get a hundred 1 level classes. Of course there are some 'optimized' class builds discovered by players. In other words, it was a system where it was impossible to have completely identical characters unless you intentionally made them so.

Depending on the skills and abilities they possessed, players can picked up different pieces of additional information upon exploring a new area. For example, such classes like alchemists and herbalists, with their herbalogical skills, would be able to learn about the various herbs that they could harvest in the area.

Guild
Guild can conquer a dungeon and use the place as it's headquarters. In this case, the guild is granted NPCs to protect its base. There are three categories of these NPCs. There were guilds that also conquered and used a city as their base in YGGDRASIL. It was a common occurrence for different guilds to lay siege to a city. Ainz stated that setting up a base in a city would make some of the areas hard to defend against.
 * Spawn NPCs pop-up automatically from the dungeons. They don't need gold to summon or maintain, yet they are under 30-level and do not have enough power to protect the stronghold.
 * Mercenary NPCs can be summoned by spending guild finances. In addition, the mercenary system that summoned creatures in exchange for YGGDRASIL currency did not allow for the summoning of Death Knights. One good thing about them was that it could allow a solo player to form a group, but their AI was not very good, and their combat ability was lower than even a poorly put-together character of the same level. Upon grouping with such NPCs, people who aren't good enough were hindered when running difficult dungeons.
 * Custom NPCs can be customized freely, with their power level depending of the level of the guild stronghold. The lowest-ranked guild headquarters provides 700 level to be shared between NPCs. This can be increased by upgrading to an higher-ranked dungeon, using cash, etc. Customization tools includes not only level, equipment, and appearance but also AI. Thus custom NPCs can be made and used as powerful guardians. Of course a guild is totally free to customize it's NPCs just for decoration purpose.

Magic
More than 6,000 different spells exist in YGGDRASIL. A level 100 spell caster usually knows around 300 of them (3 x caster level in the Web Novel.). Even basic functions such as message needs spells to use, so most of the spell casters have trouble managing all the spell they desire to have.

Magic is divided into eleven ranks: From Rank 1 to 10 and exceeding pass it is Overrank Magic. Overrank magic has miraculous power that is even compared to 10th rank Magic, but suffers from huge casting and cool down time, preventing the frequent use of it. Casting overrank magic decreases the caster's defense while receiving a certain amount of damage cancels the casting.

Items
Items are classified accordingly to the following rank system: Items are drop as a data crystal from monsters, and players can produce items freely in the capacity of crystals, including options to customize their appearance and name. In order to make one such as weapons and armor, it is through inserting a data crystal into an item skin. Most players named their equipment in reference to legends and mythologies, in order to make them an easier profit to sell.
 * Low → Middle → High → Top → Legacy → Relic → Legendary → Divine
 * Artifacts are not in anyways related to specific ranks. It just means they are items with fixed data. Therefore, artifacts with low rank can also exist.

The smith was also a key part of the equation. In YGGDRASIL, the humanoids called Dwarves had bonuses to craftsman-type classes to craft these weapons.

World Class Items are items, whose power overrides the limit of other items. Many of them can ignore or even change the game system of YGGDRASIL.

Monsters
The most powerful monsters in YGGDRASIL are called "World Class Enemy". Even Legion (6 parties with 6 players each) can have a hard time fighting against them. Some of them are related to World Class Items. There were about 32 level-breaking bosses and are listed below:
 * Devourer of the Nine Worlds
 * Eight Dragons
 * Seven Demon Kings of Sin
 * Ten Great Angels of the Tree of Life
 * God of the 6th Day
 * Five Rainbow Buddhas

YGGDRASIL and the New World
Once every 100 years, players of YGGDRASIL are teleported without reason into the New World. It seems that the first teleportation had occurred 600 years ago. With the knowledge and exceptional power of YGGDRASIL, the players usually shake the very foundations of that world, making them legendary godlike figures to some of the native inhabitants' view.

Ainz Ooal Gown is currently the only known player to have been teleported to the New World, when he was expecting to be forcefully logged-out of the game during the shutdown of YGGDRASIL. From this moment forward, Ainz later decided to make an everlasting name for himself in the New World he is in now.

After arriving in this world, players like Ainz felt that some of the game's functions from YGGDRASIL has been removed and he cannot access its use anymore.

Trivia

 * In Norse mythology, YGGDRASIL is the World Tree, a great ash tree located at the center of the universe and joining the Nine Worlds of Norse cosmology.
 * In YGGDRASIL, the advantageous world for heteromorphic players are Niflheim, Helheim and Muspelheim.
 * Normally, YGGDRASIL dungeons were not the sort that told you what levels were suitable for them.
 * According to Momonga, one thing that the developers of YGGDRASIL have forgotten was to make the game user-friendly for people who played it.