There are four areas of treasure chests that are connected to the Zodiac Spear, and if any of them are opened, the spear will not appear.

(1) In the "low town" directly in front of old Dalan's place.

(2) The treasure coffers in the cellars' southeast corner.

(3) The treasure coffers in the Confiscatory. This is after you recover your lost equipment in the Nalbina dungeons.

(4) There is a huge stash of sixteen treasure chests at the eastern point of Vaddu Strand (Phon Coast Region). If you have opened any of the previous chests, you only receive Gil. But the Zodiac Spear bestows 150 attack and 8 evasion.