Aincrad

Aincrad (アインクラッド) is the first «Realized World» shown in the «Sword Art Online» light novel series. Its full name is An Incarnating Radius (アン・インカーネイティング・ラディウス).

Background
Aincrad is the world set as the stage for «Sword Art Online», declared to be the world's first in VRMMORPG genre. It was incorporated in «ALfheim Online» on May 2025.

The base currency of Aincrad is the Col.

Etymology and Meaning
A «Realized World» called "An Incarnating Radius;" the name has been abbreviated as Aincrad. It is also inferable that its design is symbolic for time and space. The vertical axis represents the time and the circular floors represent the space.

Geography
Aincrad is an iron-and-stone made floating castle that has about ten kilometers floor base diameter and consists of a hundred floors stacking straight upwards, meaning that each floor's diameter is a bit smaller than the previous one. On each floor, there are a couple of large cities along with countless small scale towns and villages, forests, plains, and even lakes. Only one stairway links each floor to another, and the stairways exists beyond the boss room of each dungeons. The «Teleport Gates» of every unlocked cities are connected to one another.

Known Bosses

 * Illfang the Kobold Lord (Boss Monster of the 1st Floor)
 * Baran the General Taurus (Boss Monster of the 2nd Floor)
 * Two Headed Giant (Boss Monster of the 25th Floor)
 * Ant Queen (Boss Monster of the 46th Floor)
 * Six-Armed Metalic Statue Buddah (Boss Monster of the 50th Floor)
 * The Geocrawler (Boss Monster of the 56th Floor)
 * The Gleam Eyes (Boss Monster of the 74th Floor)
 * The Skull Reaper (Boss Monster of the 75th Floor)
 * Heathcliff (Supposedly, the Boss of the 100th Floor)
 * Nicholas the Renegade (Boss Monster of the Lost Forest in Christmas Event)
 * The Fatal Scythe (Boss Monster of the Black Iron Castle Hidden Bonus Dungeon)

Known Monsters

 * Blue Slug
 * Dark Elf
 * Demonic Servant
 * Drunken Apes
 * Dusk Lizard
 * Elder Treant
 * Feathery Dragon (Pina)
 * Flower Monster
 * Walking Flower
 * Forest Elf
 * Four Eyed Frog
 * Frenzy Boar (Level 1)
 * Frost Dragon
 * Gargoyle
 * Giant Venus Fly Trap
 * Jagged Worm
 * Killer Mantis
 * Kobold
 * Land Anemone
 * Large Nepent
 * Little Nepent
 * Lizardman Lord (Level 82)
 * Lungfish
 * Pup
 * Ragout Rabbit (Super Rare)
 * Ruin Kobold Sentinel
 * Ruin Kobold Trooper
 * Storm Hornet
 * Treant Sapling
 * Trembling Cow
 * Trembling Ox
 * Wind Wasp
 * Wolf

Known Plants

 * Pneuma Flower

New Aincrad (ALO Version)
At the end of Fairy Dance Arc (Alfheim Online), with the sprouting of the «World Seed», some of the old ALO players funded a new company, Ymir, which bought all of the ALO data from RECTO for a small fee and discovered that a complete copy of the castle existed on the server. As the company had to fight a decrease in the playerbase due to RECTO Progress' human experiments and because the company was formed by veteran MMO players who had been playing 2D age and couldn't bear the deletion of the intricately designed castle, the castle of New Aincrad was implemented into the ALO world on May 2025. The castle is essentially identical to the original Aincrad, except for a few key features.

First, the bosses and dungeon monsters were made significantly more difficult, as there is no threat of real death in the ALO's Aincrad. Dungeon maps, bosses, and similar features were likely re-done, as the Clearers in ALO continue to utilize mapping and scouting strategies on bosses. The last known change is on the Monument of Life. After this update, the monument, which before used to list existing players who were still alive at the time, is now  called as the «Monument of Swordsmen » and used to list players who participate in clearing the boss of each floor. As the monument can only record 7 player names for each floor cleared at most due to space limitations, if more than 1 party participates in the battle against the boss of the floor, only the name of the leader of each party will be listed on the monument, however, if 1 party of up to 7 players is able to beat the boss on their own, the name of each member of the party will appear on the monument.

Since Aincrad was fused with ALfheim Online's gameplay, the system was also designed to re-account for magic, flying, and the new limitations and additions with Sword Skills. It is now possible to fly from floor to floor in ALO's Aincrad, though there is an invisible wall at the highest front line floor, preventing access via flight to floors that have not yet been unlocked. Dungeons are no-flying zones, and the remain-light system was incorporated from ALO.

It is currently being cleared by guilds and the like, led by high level players like General Eugene.