|Spoiler Alert: This article or section contains details about plotlines not covered in the anime. Do not proceed unless you wish to be spoiled. |
A Boss, in video game terminology, is a unique computer-controlled monster or character that is much more powerful than an average monster or non-player character encountered in the game until that point and usually serves as a challenge to the player at the end of a particular section of a game, usually a level or stage, or guarding a specific objective.
In the Sword Art Online Universe
Throughout the Sword Art Online series, there are several types of bosses that can be encountered: Floor Bosses, Mid-Bosses, Field Bosses, Flag Mobs and Dungeon Bosses. Most, but not all, bosses within the series, especially Floor Bosses, have "the" in their name to signify their uniqueness as bosses.
A Floor Boss (フロアボス, Furoa Bosu?), alternatively called a Labyrinth boss, is a type of boss that can only be encountered in a large room, called a boss room, on the 20th floor of a Labyrinth in the castle of Aincrad. A Floor Boss's main purpose is to guard the entrance to the next floor, requiring players to defeat it to advance towards the 100th Floor. Each Floor Boss is a powerful creature, with several Hit Point (HP) bars, and usually has special attack patterns that are activated once the monster’s HP falls below a certain level. Some Floor Bosses also have minions that are constantly summoned throughout the battle to aid it in dealing with the players, though some bosses do not have minions at all.
The difficulty of each Floor Boss varies from floor to floor, with some causing little to no trouble, like the boss of the 22nd Floor, while others are extremely dangerous. The bosses on Aincrad's quarter floors are especially powerful and have led to numerous deaths in Sword Art Online. Normally, players may retreat from boss rooms by either using Teleport Crystals or retreating via the door if they can reach it in one piece, as bosses never leave the rooms they reside in, however, the boss rooms of the 74th and 75th Floors are designated as Anti-Crystal Areas, and it can be presumed that the remaining floors also host such effect, while the boss rooms starting with the 75th Floor automatically seal the players in a few minutes after they enter the room, completely preventing the chance of retreat during the battle.
Floor Bosses are also present in New Aincrad in New ALfheim Online. However, all of the Floor Bosses of the original Aincrad were replaced with brand new bosses that, due to ALfheim Online not being a death game, are usually much more powerful than their counterparts in the original Aincrad. Like in the original Aincrad, there are exceedingly strong monsters every set number of floors; however, in New Aincrad, such a boss appears on every tenth floor instead of every twenty fifth. Floor Bosses within New Aincrad also have their HP bars hidden from the players to make the battles even more difficult by making it harder to judge how much HP the boss has remaining. All boss rooms automatically seal the players in within a minute after they enter the room, with players even having the option to seal the boss rooms earlier by pressing a stone button on the wall next to the door.
Additionally, a new feature called the Monument of Swordsmen replaced the Monument of Life in New Aincrad. This new monument records the names of the players that participate in defeating a Floor Boss. However, as the monument is a 3D object within the world and hold a limited number of names in total, while it has to suffice for 100 floors, thus only the names of the party leaders that partake in the raid against the Floor Boss are added to the monument. Though, if a party of seven members or less manages to defeat the boss without any reinforcements, all the names of the members in that party are recorded on the monument.
Most Floor Bosses are best dealt with when the raiding party has as many players participating as possible, though there is an upper limit of up to forty-eight players in a single raiding party in Sword Art Online[† 1] and up to forty-nine players in New Aincrad in ALfheim Online[† 2].
Known Floor Bosses
|Original Aincrad Bosses|
|Illfang the Kobold Lord||イルファング・ザ・コボルド・ロード||1||Defeated on December 4, 2022|
|Asterius the Taurus King||アステリオス・ザ・トーラスキング||2||Defeated on December 14, 2022|
|Nerius the Evil Treant||ネリウス・ジ・イビルトレント||3||Defeated on December 21, 2022|
|Wythege the Hippocampus||ウィスゲー・ザ・ヒッポカンプ||4||Defeated on December 27, 2022|
|Fuscus the Vacant Colossus||フスクス・ザ・ヴェイカントコロッサス||5||Defeated on December 31, 2022|
|The Irrational Cube||ジ・イレーショナル・キューブ||6||Defeated on January 4, 2023|||
|Kagachi the Samurai Lord||カガチ・ザ・サムライロード||10|||
|The Storm Griffin||ザ・ストームグリフィン||11|||
|The Strict Hermit||ザ・ストリクトハーミット||12|||
|The Dire Tusk||ザ・ダイアータスク||18|||
|Waheela the Black Wolf||ワヒーラ・ザ・ブラックウルフ||28|||
|Bracken the Prison Warden||ブラッケン・ザ・プリズンワーデン||40||Defeated on October 18, 2023|||
|Six-armed metallic Buddha statue||N/A||50||Drops: Elucidator|
|Armoured stone warrior||N/A||60|
|The Gleam Eyes||ザ・グリーム・アイズ||74||Defeated on October 18, 2024|
|The Skull Reaper||ザ・スカル・リーパー||75||Defeated on November 7, 2024
Casualties: 10 (scouts) + 14 (boss battle)
|Dorz'l the Chaos Drake||ドルゼル・ザ・カオスドレイク||91||N/A|||
|Superseded Aincrad Bosses|
|Baran the General Taurus||バラン・ザ・ジェネラルトーラス||2||N/A|
|N/A||The Irritating Cube||ジ・イリテーテイング・キユーブ||6||N/A|
|An Incarnation of the Radius||アン・インカーネイト・オブ・ザ・ラディウス||100||N/A|
|New Aincrad Bosses|
|N/A||Wadjet the Flaming Serpent||ワジェト・ザ・フレイミング・サーペント||8|
|The Four-Armed Giant||N/A||27||Defeated on January 8, 2026|
In Sword Art Online, a Mid-Boss (中ボス, Chū Bosu?) is a boss-class monster that impedes travel between the floors of a Labyrinth Tower or a boss-class monster that supports the Floor Boss. Unlike regular Floor Boss minions, Mid-Bosses grant a Last Attack Bonus on defeat.
|Nato the Colonel Taurus||ナト・ザ・カーネルトーラス||In the 2nd Floor boss room.||Defeated on December 14, 2022|
|Baran the General Taurus||バラン・ザ・ジェネラルトーラス||In the 2nd Floor boss room.||Defeated on December 14, 2022
Drops: Gold bull-pattern boxers
|N/A||Ophidian-type boss||N/A||5th floor of the Labyrinth.||Defeated on January 4, 2023|||
|Ruthless Warder Chief||ルースレス・ワーダーチーフ||The stairway between the 23rd and 24th floors of the Labyrinth on the 40th Floor of Aincrad.||Defeated on October 15, 2023|||
A Field Boss (フィールドボス, Fīrudo Bosu?) is a named monster strategically placed at the entrance to a Labyrinth on most floors in Aincrad. The main function of this Boss is to prevent access to the Labyrinth of the floor until the monster is defeated. A Field Boss's den is usually surrounded by cliffs or ranging streams on both sides, arranged in such a way that there would be no way to access the Labyrinth until the Boss is defeated. Like Floor Bosses, each Field Boss can only be defeated once, however, they are much easier to defeat and can be defeated by a single party, if all members are sufficiently leveled and have enough experience in battle.
Not all floors have a field boss. For example the 1st Floor and the 22nd Floor did not have any.
Known Field Bosses
|Bullbous Bow||ブルバス・バウ||2||Defeated on December 9, 2022
Drops: Chakram[† 3]
|Biceps Archelon||バイセプス・アーケロン||4||Defeated on December 24, 2022|
|N/A||Vine plant-type Field Boss||N/A||6||Defeated on January 2, 2024
Drops: A large amount of peas.
|N/A||Basalt Morpha||バサルトモルファ||6||Defeated on January 4, 2024|||
|N/A||Carnivorous plant-type Field Boss||N/A||6||Defeated on January 4, 2024|||
|Zehghi the Flame Caller||ゼーギ・ザ・フレイムコーラー||11|||
|Geocrawler||ジオクロウラー||56||Defeated on March 7, 2024|
A Flag Mob (フラグ Mob, Furagu Mob?) is a monster set up for the completion of a quest or event. These type of monsters can spawn between every few hours to every few days, while some Flag Mobs only spawn once a year or do not re-spawn at all. Some rare Flag Mobs that are as powerful as a Boss monster usually also drop rare and valuable items upon being killed, while other Flag Monsters are barely more difficult than a regular monster. Some Flag Mobs are part of quests that have sub-routes, thus a certain event may be triggered during the quest that would help defeat the boss, for example, taking a certain sub-route may lead to a temporary NPC partner for the quest.
Known Flag Mobs
|Sword Art Online|
|Nephila Regina||ネフィラレジーナ||In the Queen Spider Nest on the 3rd Floor.||A dungeon boss that needs to be killed for the «Vanquishing the Spiders» quest.|
|Fallen Elf Commander||フォールン・エルフ・コマンダー||3rd Floor||The boss that needs to be defeated for the «Retrieving the Key» quest.|
|The King of Lakes||湖のヌシ||Lake on the 22nd Floor||A fishing event boss that drops a rare fishing rod.||Rare fishing rod|
|The Witch of the West||西の魔女||Quest area on the 22nd Floor||A boss that is required to be killed for the «Witch of the West and the Three Treasures» quest.|
|Nicholas The Renegade||背教者ニコラス||Forest of Wandering||Christmas event boss that drops a revival item called Divine Stone of Returning Soul.||Divine Stone of Returning Soul|
|Kraken the Abyss Lord||クラーケン・ジ・アビスロード||Undersea Temple||The NPC that gives players the «Deep Sea Plunderers» quest to steal the Prince's Egg from the Undersea Temple and becomes a boss if the players refuse to turn in the egg.|
|Thrym||スリュム||Thrymheim||The boss required to be killed for the completion of «The Holy Sword of the Ice Palace» quest.|
A Dungeon Boss is a stronger than average and, usually, named monster that appears in dungeons (field dungeon/sub-dungeon) to either impede player progress towards clearing the dungeon, for example, by guarding the stairs to the next floor of the dungeon, or for guarding the treasure at the end of the dungeon. Some Dungeon Bosses also double as Flag Mobs for certain quests, like in Thrym's case, while some were meant to ensure that players could never access special areas of a dungeon.
Known Dungeon Bosses
|Sword Art Online|
|Nephila Regina||ネフィラレジーナ||In the Queen Spider's Nest on the 3rd Floor|
|Feral Warder Chief||フィーラル・ワーダーチーフ||A dungeon on the 40th Floor.||Casualties: Yuna|||
|X'rphan the White Wyrm||白竜ゼーファン||West Mountain|
|The Fatal Scythe||ザ・フェイタルサイズ||Hidden Dungeon|
|Cyclops||N/A||Thrymheim's 1st floor|||
|Black Minotaurus||?||Thrymheim's 2nd floor.|
|Golden Minotaurus||?||Thrymheim's 2nd floor.|
|Centipede-like giant||N/A||Thrymheim's 3rd floor|
|Thrym||スリュム||Thrymheim final floor|
- ↑ The Day After
- ↑ Author's commentary Part 1 and Part 2.
- ↑ Tweet by the author
- ↑ Progressive Volume 6, Canon of the Golden Rule, Part 15
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Full Record of SAO the Movie "Behind-the-Scenes" (8th week Ordinal Scale movie bonus)
- ↑ 6.0 6.1 Hopeful Chant Part 5
- ↑ Volume 10, Chapter 4, Part 3
- ↑ Volume 1, Chapter 20
- ↑ Volume 1, Chapter 21
- ↑ Volume 1, Chapter 22
- ↑ 11.0 11.1 Hopeful Chant Part 1
- ↑ 12.0 12.1 Progressive Volume 1, Rondo of a Fragile Blade, Part 12
- ↑ 13.0 13.1 13.2 Progressive Volume 6, Canon of the Golden Rule, Part 13
- ↑ Progressive Volume 5, Canon of the Golden Rule, Part 5
- ↑ Volume 8, Calibur Part 3