A boss battle is a frequent occurrence in both video and computer games. A boss battle can occur at the end of a video game, and must be won in order for the game to be considered finished. More frequently, a video game will have many a boss battle, as the game gets progressively more difficult.
Particularly adventure or fantasy games, and run and shoots, will probably have multiple bosses. In a run and shoot, a boss battle may occur in order to gain access to the next level of the game. For example, in the original Sega version of Sonic the Hedgehog, Sonic had to undertake a boss battle each time three levels of the game were completed. This would then result in a new themed three level section, called a "zone."
In fantasy or adventure games, sections of the game may end with a boss battle. Generally these battles are helpful since they increase the experience points of the fighter or fighters involve, which would make them better fighters for harder sections.
This is particularly the case with the Final Fantasy Series and other games like the Shining Force Series. Most sections, and access to more difficult areas have to be gained by winning a boss battle. Further, winning the boss battle tends to result in huge gains in experience points so that characters are ready to fight more difficult monsters.
Some video games like the Zelda series for Nintendo have simplified the experience points resulting from a boss battle. Instead the Zelda fighters may gain extra life points, usually shown as hearts, and as well may get useful items from a boss battle. The principal behind the Final Fantasy type boss battle experience points is that these are similar to the old games like Dungeons and Dragons that inspired fantasy video games. In these games, successful battles meant a player’s characters became more adept, the longer they played the game.
Conversely, in a run and shoot game, playing the game longer generally means the player has acquired better skill at playing the game and can thus tackle a boss battle. It is the player and not the character that must become more adept to win at harder boss fights.
The term boss battle does not always mean that a violent battle or killing takes place. In general, the boss battle fights of the early Sonic games were simply bouncing into Dr. Robotnik, until he went away. He was defeated temporarily but not permanently.
Many E-rated games have some variant of the boss battle but involve neither the death of characters nor the death of bosses. In fact some use the euphemism “KO” or knocked out instead of dead. On the other hand, T-rated or M-rated games generally employ battle in its most literal sense and can run amok with blood and gore as the result of a boss battle.