They're are four chests you DON'T WANT TO OPEN in the game. One is opposite of Dalan's house. Another is in the right side of the cellar, where all the servants are(when you're sneaking into the palace.) Another is in the weaponry when you get your stuff back on the escape from Nalbina. The last is among a group of sixteen chests, each housing some Gil. If you can avoid these, you can get the Zodiac Spear. Of course, saving up to it was the easy part, GETTING to it is a whole 'nother story!