Bosses are stronger, tougher and more difficult to defeat than regular monsters, which are provided solely for the player to use to gain experience and levels. The player needs these levels to in turn be able to defeat boss monsters and progress the story.

Defeating a boss usually yields a large amount of experience itself as a way to kick-start the next section of grinding before the next boss, and the process repeats itself until the final boss is slain and the game ends.