"Castlevania III: Dracula's Curse (悪魔城伝説, Akumajō Densetsu,? "The Legend of the Devil's Castle") is the third and final Castlevania video game produced for the Nintendo Entertainment System.
The plot of Castlevania III: Dracula's Curse is a prequel to the original Castlevania (much like the earlier Game Boy game Castlevania: The Adventure) set a few centuries before the events of the original game. The game's protagonist is Trevor C. Belmont, an ancestor of the original hero Simon Belmont.
Castlevania III abandons the adventure game elements of its immediate predecessor and returns to the platform game roots of the first Castlevania title. Unlike Castlevania, however, Castlevania III is not strictly linear: Trevor, the main character, can be assisted by one of three possible assistant characters, and after completing the first level, and at several other points throughout the game, the player is given a choice of paths to follow. The choices made by the player in these circumstances can have a profound impact on how the game unfolds. There are 15 stages in total.
Castlevania III was the first game to use Konami's VRC6 chip, which is included in the cartridge to provide the console more capabilities. The VRC6 chip primarily added three audio channels to the system--allowing the game to use eight audio channels--as well as provide smoother animation for sprites. The game's audio programmer, Hidenori Maezawa, assisted in the chip's creation. The North American release replaced the VRC6 with Nintendo's Memory Management Controller (MMC) chip, specifically the MMC5 model. The MMC5 chip lacked the extra audio channels, and the game's music had to be downgraded to comply with the NES's standard five channels."
Source: Wikipedia, "Castlevania_III:_Dracula's_Curse," available under the CC-BY-SA License.