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This page is about Aincrad, the floating castle in Sword Art Online and the New Aincrad in ALfheim Online. You maybe looking for the Aincrad Arc or the manga adaptation named as Aincrad.
Warning Spoiler Alert: This article/section contains details about future plotlines described in the light novels, not covered in the anime. Do not proceed unless you want to be spoiled.






Location Information
Controlled By

Kayaba Akihiko (SAO)


Volume 1


Aincrad Manga Stage.001


Episode 1

Aincrad (アインクラッド, Ainkuraddo?) is the first «Realized World» shown in the Sword Art Online series and the stage for the first VRMMORPG, «Sword Art Online», created by Kayaba Akihiko. It later became one of the nine realms of New ALfheim Online and the stage for the game's second Grand Quest.


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

The base currency of Aincrad is the Cor.

Etymology and MeaningEdit

The castle's name came from the concept of a «Realized World», called An Incarnating Radius (アン・インカーネイティング・ラディウス, An Inkāneitingu Radiusu?), which has been abbreviated as Aincrad.[1] It is also inferable that its design is symbolic for time and space. The vertical axis represents time and the circular floors represent space.[2]


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 exist beyond the boss room of each Labyrinth. The «Teleport Gates»[3] of every unlocked cities are connected to one another.

It is possible to climb the outer circumference of Aincrad, but trying to climb beyond a floor that has not been unlocked will result in being blocked by a barrier and a visual error.[4]

Aincrad Locations Navigation Bar
Teleport Gate
Floor Notable locations and landmarks
1 Starting CityBlack Iron Palace, Hidden DungeonMonument of Swordsmen[Navbar 1]Monument of Life[Navbar 2]Chamber of Resurrection[Navbar 3]TolbanaHorunka Village
2 Urbus, Urbus Teleport Gate Plaza, Marome Village, Taran Village
3 Forest of Wavering Mist
4 Lobria, Lobria Teleport Gate Plaza
7 Monster Arena
8 Frieven Village, Frieven Teleport Gate Plaza
10 Thousand Snake Castle
11 Taft, Taft Teleport Gate
19 Ralberg, Ralberg Teleport Gate, Hill of the Cross, Griselda's Tomb
20 Sunshine Forest
22 Coral Village, Coral Teleport Gate Plaza, Forest House K4, Lake Outside Coral Village,
24 Panareze, Panareze Teleport Gate Plaza
27 Ronbaru Town, Ronbaru Teleport Gate
28 Wolf Plains
35 Forest of WanderingMishe, Mishe Teleport Gate Plaza
39 Former location of the Knights of Blood Headquarters
46 Ant Hill
47 Floria, Floria Gate Plaza, Hill of Memories, Forest of Giant Flowers
48 Lindarth, Lindarth Teleport Gate Plaza
49 Myujen, Myujen Teleport Gate Plaza
50 Algade, Algade Teleport Gate Plaza
55 Granzam, Granzam Teleport Gate Plaza, Knights of Blood Headquarters, West Mountain
56 Pani, Divine Dragon Alliance Headquarters
57 Marten, Marten Teleport Gate Plaza
59 Danac, Danac Teleport Gate Plaza
61 Selmburg, Selmburg Teleport Gate Plaza
65 Old Castle Labyrinth
66 Old Castle Labyrinth
74 Kamdet, Kamdet Teleport Gate Plaza
75 Collinia, Collinia Teleport Gate Plaza
100 Ruby Palace
  1. only in New ALO
  2. only in the SAO official service
  3. only in the SAO Beta


A variety of unique monsters that can be found on every floor and in every dungeon in Aincrad. They are the main source of income for most players, as they drop Cor and other items to the victorious players. Like NPCs, monsters, except for most if not all Bosses, re-spawn after a certain amount of time has passed since they were killed.

Known BossesEdit

Boss Name Floor Other Details
«The Fatal Scythe» 1st Floor (Bonus) Boss Monster of the Black Iron Palace Hidden Bonus Dungeon[4]
«Illfang the Kobold Lord» 1st Floor
«Nato The Kernel Taurus» 2nd Floor Spoiler Alert!
«Baran the General Taurus» 2nd Floor Spoiler Alert!
Closed Beta Floor Boss
Mid-boss in the death game
«Asterios The Taurus King» 2nd Floor Spoiler Alert!
Floor Boss in the death game
«Bullbous Bow» 2nd Floor (Field) A Field Boss of the 2nd Floor.
«Nephila Regina»[5] 3rd Floor (Dungeon)
«Fallen Elf Commander»[6] 3rd Floor (Quest)
«Nerius the Evil Treant»[7] 3rd Floor Quest boss for the 3rd Floor portion of the first campaign quest in SAO.
«The Witch of the West» 22nd Floor (Quest) Can only be defeated with the help of the roar of a lion.
Two-Headed Giant 25th Floor
Metallic Elemental 27th Floor
«Nicholas The Renegade» 35th Floor (Event) A Christmas event Flag Mob in the Forest of Wandering[8]
Six-Armed Metallic Buddha Statue 50th Floor
«X'rphan the White Wyrm» 55th Floor (Quest)[9]
«Geocrawler» 56th Floor (Field) A Field Boss of the 56th Floor.
Armored Stone Warrior 60th Floor[10]
«The Gleam Eyes» 74th Floor[11]
«The Skull Reaper» 75th Floor[12]
Heathcliff 100th Floor (supposedly)

Known MonstersEdit

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Missing Information: Reformatting Lists to Tables
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  • Ant queen (46th Floor) [13]
  • «Bull Slug» (ブルスラッグ, Buru Suraggu?) (61st Floor) [14]
  • «Dark Dwarf Miner» (27th Floor - Labyrinth) [15]
  • «Blood Wolf Leader» (28th Floor) [16]
  • Coppice Spider [17]
  • «Dark Elven Wolf Handler» (黒エルフの狼使い(ダークエルブン・ウルフハンドラー), Dāku Erubun Urufu Handorā?, lit. "Dark elven wolf user") (3rd Floor) [18]
  • «Dark Elven Royal Guard» (ダークエルブン・ロイヤルガード, Dāku Erubun Roiyaru Gādo?) (3rd Floor)[19][† 1]
  • «Demonic Servant» (74th Floor - Labyrinth) [11]
  • «Drunk Apes» (35th Floor) [20]
  • «Dusk Lizard» (ダスクリザード, Dasuku Rizādo?) [21]
  • «Elder Treant» (エルダー・トレント, Erudā Torento?) (3rd Floor) [22]
  • Elder Sapling [17]
  • «Fallen Elf Warrior» (フォールン・エルフ・ウォリアー, Fōrun Erufu Uoriā?) [6]
  • «Feathered Little Dragon» [20]
  • «Forest Elven Hallowed Knight» (フォレストエルブン・ハロウドナイト, Foresuto Erubun Haroudo Naito?) (3rd Floor) [23][† 2]
  • «Forest Elven Falconer» (森エルフの鷹使い(フォレストエルブン・ファルコナー), Foresuto Erubun Farukonā?, lit. "Forest Elven Falcon user") (3rd Floor) [18]
  • «Frenzy Boar» (Level 1) (1st Floor)[24]
  • «Frost Bone» (フロストボーン, Furosuto Bōn?) (55th Floor) [9]
  • Gargoyle (27th Floor) [25]
  • «Garish Gerbera» (47th Floor) [26]
  • Giant Venus Fly Trap (47th Floor) [27]
  • «Granite Elementals» (27th Floor - Labyrinth) [15]
  • «Jagged Worm» (ジャグド・ワーム, Jagudo Wāmu?) (2nd Floor)[28]
  • «Killer Mantis» (20th Floor) [16]
  • Land Anemone (47th Floor) [26]
  • «Large Nepent» (ラージネペント, Rāji Nepento?) (1st Floor) [29]
  • «Lesser Taurus Striker» (2nd Floor)[30]
  • «Little Nepent» (Level 3) (1st Floor) [29]
  • «Lizardman Lord» (Level 82) (74th Floor - Labyrinth) [31]
  • «Maroon Wolf» (22nd Floor) [32]
  • «Ragout Rabbit» (Super Rare) (74th Floor) [21]
  • «Red Spotted Beetle» (レッド・スポテッド・ビートル, Reddo Supoteddo Bītoru?) (2nd Floor)[33]
  • «Ruin Kobold Sentinel» (1st Floor) [34]
  • «Ruin Kobold Trooper» (1st Floor - Labyrinth) [35]
  • «Scavenger Toads» (1st Floor) [10]
  • «Storm Hornet» (ストームホーネト, Sutōmu Hōneto?) (2nd Floor) [28]
  • Swamp Kobold Trapper (1st Floor) [17]
  • «The King of Lakes» (22nd Floor - event monster) [36]
  • «Thicket Spider» (シケット・スパイダー, Shiketto Supaidā?) [† 3] (3rd Floor) [37]
  • «Treant Sapling» (トレント・サプリング, Torento Sapuringu?) (3rd Floor) [38]
  • «Trembling Cow» (トレンブリング・カウ, Toremburingu Kau?) (2nd Floor) [39]
  • «Trembling Ox» (2nd Floor) [40]
  • Werelions[† 4] (40th Floor) [41]
  • Werepanthers[† 4] (22nd Floor - quest area) [41]
  • «Wind Wasp» (2nd Floor) [28]
  • «Dire Wolf» (1st Floor) [42]

New Aincrad (ALO Version)Edit

Aincard in ALO

Aincrad in ALfheim Online

At the end of Fairy Dance Arc, with the sprouting of the «World Seed», some of the old ALO players funded a new company, Ymir, which bought all of the ALfheim Online data from RECT Progress Inc. 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 RECT Progress' inhuman experiments and because the company was formed by veteran MMO game players who had been playing since the 2D age and could not bear the deletion of the intricately designed castle, the castle of New Aincrad was implemented into the ALO world, floating above the continent of Alfheim, on May 2025.

The castle is currently being cleared by guilds and players without a guild. Such raids are led by high-level players like General Eugene


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 and similar features were likely re-done, as the Clearers in ALO continue to utilize mapping and scouting strategies on bosses, while all the bosses were changed to brand new ones. 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 is used to list players who participate in clearing the boss of each floor. As the monument can only record seven player names for each floor cleared at most (due to space limitations), if more than one 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 one party of up to seven players is able to beat the boss on their own, the name of each member of the party will appear on the monument.[25]

Features and RestrictionsEdit

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, although the outer circumference is closed for floors which have not yet been unlocked.[15] Additionally, a flight altitude limit for players is set at the level of the 50th Floor, preventing players from examining the outside of the floors above it, including the top of the castle.[15][43] Dungeons are no-flying zones, and the Remain Light system was incorporated from ALO.

Known BossesEdit

Boss Name Floor Other Details
Wadjet the Flaming Serpent 8th Floor
The Four-Armed Giant 27th Floor Non-official name
Large Crustacean[44] 28th Floor Non-official name



  1. Named as "Dark Elf Sentry" in the web version.
  2. Named as "Forest Elf Officer" in the web version.
  3. Written in English with furigana in the raw
  4. 4.0 4.1 A monster race, not the name of an individual monster


  1. Volume 8, Calibur
  2. Volume 5, Chapter 2
  3. Volume 1, Prologue
  4. 4.0 4.1 Volume 2, Morning Dew Girl
  5. Progressive Volume 2, page 106
  6. 6.0 6.1 Progressive Volume 2, page 362
  7. Progressive Volume 2
  8. Volume 2, Red-nosed Reindeer
  9. 9.0 9.1 Volume 2, Warmth of the Heart
  10. 10.0 10.1 Volume 2, Morning Dew Girl Part 3
  11. 11.0 11.1 Volume 1 Chapter 9
  12. Volume 1 Chapter 21
  13. Volume 2, Red-nosed Reindeer, Part 1
  14. Volume 4, Chapter 6
  15. 15.0 15.1 15.2 15.3 The Day After
  16. 16.0 16.1 Episode 3
  17. 17.0 17.1 17.2 Monochrome Concerto
  18. 18.0 18.1 Progressive Volume 2, page 70
  19. Progressive Volume 2, page 41
  20. 20.0 20.1 Volume 2, The Black Swordsman, Part 1
  21. 21.0 21.1 Volume 1, Chapter 5
  22. Progressive Volume 2, page 25
  23. Progressive Volume 2, page 31
  24. Volume 1, Chapter 2
  25. 25.0 25.1 Volume 7, Chapter 3
  26. 26.0 26.1 Volume 2, The Black Swordsman, Part 3
  27. Episode 4
  28. 28.0 28.1 28.2 Progressive Volume 1, Chapter 2, Part 2
  29. 29.0 29.1 First Day
  30. Progressive Volume 1, Rondo of the Transient Sword, Part 8
  31. Volume 1, Chapter 1
  32. Material Edition 11
  33. Progressive Volume 1, Chapter 2, Part 1
  34. Progressive Volume 1, Chapter 1, Part 6
  35. Progressive Volume 1, Chapter 1, Part 1
  36. Volume 1, Chapter 19
  37. Progressive Volume 2, page 77
  38. Progressive Volume 2, page 24
  39. Progressive Volume 1, Chapter 2, Part 3
  40. Progressive Volume 1, Intermission - Reason for the Whiskers
  41. 41.0 41.1 The Day Before
  42. Episode 1
  43. Author's commentary
  44. Volume 7 Chapter 10


ALfheim Online Locations Navigation Bar
Midgard New Aincrad - See Aincard Location Navigation Bar for locations in new Aincrad
World Tree Alne - Virtual Lab(Floating City) - Yggdrasil City
Alfheim Ancient Forest - Butterfly Valley - Swilvane - Legrue Corridor - Legrue - Thule Island - Undersea Temple
Jötunheimr Great Void - Thrymheim

Start a Discussion Discussions about Aincrad

  • Bosses

    3 messages
    • Some information on Progressive Volume 2 but I forgotten about them...
    • A raid group is only required for floor bosses. Field bosses can be handled with a party or two, depending on how strong the members of the pa...
  • So should SAO:IM floor, boss info add in to the list?

    3 messages
    • and why some boss in the article donot have "the" in their name...
    • Don't turn the first sentence into a title. Titles are supposed to be a short name for the topic, not the whole idea in it. On topic, Infin...

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