Characteristics
Bosses are usually significantly superior to regular enemies, and are usually found at the end of a level or area. Most games also include a "final" boss, which is usually the main antagonist in the story, at the very end of the game. Some examples include Ganondorf from the Zelda saga, Bowser from the Mario franchise and Doctor Wily from Mega Man. While most games include a mixture of boss opponents and regular opponents, some games have only regular opponents and some games have only bosses – for example, Shadow of the Colossus has no enemies other than bosses. In games such as Duke Nukem 3D, the first boss even reappears throughout the game as an uncommon enemy. However, they are weaker than the original. In a similar vein, a relatively powerful enemy may be introduced via a boss battle, but later appear as an uncommon but strong enemy, after the player has had a chance to find more powerful weaponry or a weakness it may have. An example of this is in Castlevania: Order of Ecclesia, where the game's second boss, the Giant Skeleton, reappears in later areas as a normal enemy, with the player even fighting two at once at one point.
Boss battles are typically seen as dramatic events. As such, they are usually characterized with unique music, and/or cutscenes before and after the boss battle. Recurring bosses and final bosses may have their own specific theme music, to distinguish them from other boss battles.
Some bosses require the player to defeat them in a certain way that may be unusual to normal attacks, such as requiring the player to use a certain weapon, such as in Super Ghouls 'n Ghosts, or hitting the boss in a certain area, termed a "weak point", such as in the Metroid series. Story-centered bosses of this type will sometimes require certain prerequisites to be performed during the fight for the player to succeed, such as a requirement that a partner must stay alive during the battle or sequence to be counted as a victory. The most common games that have these requirements are the games in the Grand Theft Auto franchise, which players can usually have a partner during a mission that they must protect; the final mission of Grand Theft Auto: San Andreas is an example of a boss battle that requires both a side character to remain alive and for additional actions to be taken in order to defeat him.
In some games, the boss returns after being defeated, sometimes in a new form with alternate attacks. This can repeat a certain number of times before the player faces their final and most powerful form. The Final Fantasy series is well known for this style of boss, often having as many as 5 phases in a single boss battle (Sorceress Ultimecia being this example; other FF villains such as Sephiroth and Vayne have from 2 to 4 stages). The Mega Man series of games also prominently display this, with the main villain (Doctor Wily; Sigma; Copy X, Elpizo, Omega, and Doctor Wiel) adopting a second and even third vehicle/body immediately after the first is destroyed to continue the fight.
As they can sustain a lot more damage than normal foes, bosses commonly have a health bar which is displayed either on/near them or in a specific location on the HUD, usually with their name or a portrait of them attached. In lieu of a health bar, some bosses, like those in the early Metroid games, change color, change attack patterns or, in the case of larger enemies, lose parts of their overall structure as they receive more and more damage. Although health bars or indicators were less common in the early days of video gaming, they are now found in many video game boss battles.
Some games also feature a sequence of consecutive boss battles as an extra challenge, sometimes known as a "Boss Rush". Boss Rush modes often include a timer and record the time taken to defeat both the singular bosses and all the bosses as a whole. Occasionally, the Boss Rush may not be a "mode" at all, instead having previous bosses placed in the game a second time, sometimes with more powerful attacks and more demanding patterns. The Mega Man series is most famous for and possibly the instigator of the Boss Rush, as every game in every series has the player fight the bosses again in the final stages just before the final boss. Gradius II, Gradius III, Gradius IV, Gradius V and Gradius Gaiden also features this.
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