This should help you with that ArmyGuy.
Rikku's God Hand:
Weapon Location: In a sealed chest at the bottom of Mushroom Rock Road, accessable by selecting Password on the airship, then inputting "GODHAND". You MUST have the Celestial Mirror in your inventory to get the weapon.
Mercury Crest location: In a treasure chest in the fourth area (see below) of Sanubia Desert, in an alcove to the northwest. If your area map is turned on, you cannot miss this.
Mercury Sigil location: Sanubia Desert, in a treasure chest in the area protected by a sandstorm. To get rid of the sandstorm, you need to play a hide-and-seek minigame with the Cactuars after you can control the airship. (You can examine the Cactuar glyph during your first visit to Sanubia Desert, but again, you cannot play the minigame until you have the airship.) First, let's get our bearings... Sanubia Desert is divided into four screens:
(1) The oasis with the save point.
(2) The winding path with the save point inside a tent.
(3) The huge open area with the ruins to the northwest and the save point next to the large Al Bhed sign in the middle.
(4) The area right before Home with the sandstorm, Cactuar glyph, antlion pits, and numerous small Al Bhed signs.
To initiate the minigame, go to the fourth area and examine the Cactuar glyph. You'll then be asked to find 10 Cactuars in the desert. After finding each one, you'll recieve a green sphere - if you managed to catch the Cactuar without it looking at you, the sphere will be named, but if not, it will be called a "Sphere del Perdedor". (In other words, "Loser Sphere".) The more named spheres that you collect, the better your prize will be. Regardless of which type of sphere you recieved, take each one back to the Cactuar glyph in the fourth area after collecting them. The order of Cactuars is is:
(1) Tomay - found in the first area, the oasis, to the right of the save point.
(2) Rovivea - running around in the northwestern alcove of the second area.
(3) Chava - hiding behind the Al Bhed 20% sign in the fourth area; examine it to find him.
(4) Alek - running back and forth in the ruins in the northwestern part of the third area.
(5) Aloja - with Alek.
(6) Vachella - hiding behind the save point inside the tent in the second area; examine it to find him.
(7) Robeya - hiding in a treasure chest in the southwestern corner of the third area. This chest contains two Mega Potions otherwise.
(8) Isrra - running around inside an antlion pit in the fourth area.
(9) Elio - at the oasis, then beams up to your airship and can be found on the roof.
(10) Flaile - appears automatically after bringing the rest of the green Cactuar spheres to the glyph.
Once you've found a Cactuar, you don't have to find them again - you can leave the desert whenever you want, and the minigame will not have reset.
Difficulty to Obtain: Easy, but time-consuming. Having the [No Encounters] auto-ability is extremely helpful in getting the Sigil. You can add this ability to an armor with 30 Purifying Salts, or win a weapon with this already added from Geosgaeno. Normally you can only put [No Encounters] on an armor, but the Geosgaeno weapon keeps the monsters away all the same.
info taken from www.kuponut.com