Monster World was once a peaceful region. Then, the peace was shattered by an invading army of monsters. A young man named Shion vowed to defeat them and make his land peaceful again.
Wonder Boy In Monster World is the third game in the Monster World spin-off series, originally known as Wonder Boy 5: Monster World 3. It puts the player in control of Shion in his quest to save Monster World from the evil hands of BioMeka. It controls like a standard platform game - run, jump, and kill enemies. The game has light RPG elements such as talking to townsfolk, collecting money to buy items, upgrading your life, and equipping a variety of armor and weapons - staying very close to the Zelda format. You can save your game to continue your quest at a later time.
Description from MobyGames