Well, I advise reading up about it. You can miss potentially the best weapon of the game by collecting specific chests. It's called the Zodiac Spear. http://www.gamefaqs.com/ps2/459841-final-fantasy-xii/answers/245867-where-are-the-chests-i-must-not-open-to-get-the-zodiac-spear Better to find a guide about it, really. It's one of the most frustrating things in Final Fantasy ever. It's counter productive, really. You generally always want to open chests in most RPGs..