Boss

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.

In Sword Art Online, the two major groups of bosses are Field Bosses and Floor Bosses. It is common knowledge that superior bosses are distinguished from weaker bosses by a definite article ("the") in their names. Such monsters are colloquially referred to as Bosses-with-THE (ザつきボス) by the players. However, unbeknownst to the majority of the player base, there are actually two types of bosses that fall under this category: ones that have a proper name before the definite article and title, and ones that do not have any proper name before the article. Contrary to expectations, bosses that do not have any proper name are actually considered more dangerous than ones that do have a proper name. According to the game's lore, these bosses were so feared by the populace that nobody even dared speak their names, which led to the names being forgotten entirely over the course of many years.

Floor Boss
A Floor Boss (フロアボス), alternatively called a Labyrinth boss, is a type of boss that can only be encountered in a boss room, a large room located on the highest 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 that are displayed over its body; special attack patterns are usually triggered once the monster's hit points fall below a certain level. However, the actual difficulty of each Floor Boss varies from floor to floor: some cause little to no trouble, such as 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. The second-most-powerful bosses are located on floors that are multiples of ten. 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.

Initially, a Floor Boss will either not be present within the Boss Room at all, or will at least passively await combat. The boss will only appear in the room or leave its passive state once a player has stepped far enough inside the room.



Normally, players may retreat from boss rooms by either using Teleport Crystals or leaving the room via the door if they can reach it safely, as bosses never leave the rooms they reside in. Upon all players leaving the room, which results in the boss disengaging from its aggressive state, all damage previously dealt to the boss will heal very quickly. Sometimes the entrance doors will lock behind players due to the boss's abilities or theme; however, the door can still be opened either by other players from the outside, or through gimmicks inside the room. Example factors that lock the door include: flooding of the room until a player opens the door from the outside, part of the boss blocking the entrance , or the door remaining sealed until a puzzle is solved. The boss rooms of the 74th and 75th Floors are designated as Anti-Crystal Areas, while the boss room of the 75th Floor also automatically sealed the players inside the room a few minutes after they entered the room, completely preventing the chance of retreat during the battle.

Following a Floor Boss's defeat, the Teleport Gate on the next Aincrad Floor will automatically open after a period of two hours, allowing public access to the new Floor from all the previously-opened lower Aincrad Floors. Alternatively, the gate may be opened early if a player reaches the main settlement of the next Aincrad Floor and touches the Teleport Gate within the two hour window. For thirty minutes or so after the players defeat a Floor Boss, the spawn rate of monsters is drastically decreased on the following Aincrad Floor. This effect is only active in the area around the main settlement of the Floor.

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 and up to forty-nine players in New Aincrad in ALfheim Online. It is possible for more players to join a boss battle and there have actually been instances where players formed two raid parties for a single boss, such as during the battle against the boss of the 25th Floor; however, it becomes harder to coordinate the players when more than one raid party is present during a battle.

Mid-Boss
In Sword Art Online, a Mid-Boss (中ボス) 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.

Field Boss
A Field Boss (フィールドボス) is a named monster strategically placed somewhere between the Teleport Gate and the entrance to each Labyrinth. The main function of these bosses are to prevent access to the Labyrinth of the floor until the monsters are defeated. A Field Boss's den is usually surrounded by cliffs or raging streams on both sides, arranged in such a way that there would be no way to access the Labyrinth until the Boss is defeated. Field Bosses can be defeated by a single party without forming a raid, if all members are sufficiently leveled and have enough experience in battle. Unlike Floor Bosses, Field Bosses can be beaten an unlimited number of times, as they respawn over time.

The number of Field Bosses on a given floor depends on the Floor's layout: the more sub-areas the Floor contains, the greater the number of Field Bosses can be expected on this Floor to demarcate them. Certain Floors are only divided into two sub-areas and thus only contain a single Field Boss, such as on the 2nd Floor. Other Floors, such as the 6th Floor, may be divided into multiple areas and thus contain multiple Field Bosses. In some cases, such as the 6th Floor, a single sub-area of a Floor may contain additional Field Bosses as well, especially when an extra boss was added as part of the changes between the beta test and full release versions of the game. On the other hand, certain outlier Floors may lack Field Bosses whatsoever, such as was the case with the 22nd Floor.

Flag Mob
A Flag Mob (フラグ 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.

Dungeon Bosses
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, such as in the case with Thrym, while some were meant to ensure that players could never access special areas of a dungeon. In Sword Art Online, regular Dungeon Bosses respawn after some time, unlike Floor Bosses and Field Bosses.