Wonder Boy in Monster World

The charmstone is available to buy in a store and it costs 500,000 gold. You could grind to 500,000 gold, however, that would take far too long so I would recommend that you find it. It is inside the pyramid but you need to have found all the Pygmy Equipment before you can get it. You then need to turn yourself into a smaller version of yourself by entering the house featured at the start of the following video.