To do this side quest get control of the airship and find the cactuar stone in the Sanubia Desert, Sandstorm area. You'll need to find the 10 little gatekeepers to obtain there spheres and enter the village. Every time you found one you have to go back to the stone so you can find the next one.

Here are the names, clues and locations of the cactuars:

#1: Tomay
Clue: Tomay's Gone. Gone to fetch the water.
Location: Near the oasis in Sanubia Desert.

#2: Rovivea
Clue: Ravivea's gone walkabout.
Location: Sanubia Desert East, to the north of the Save Sphere.

#3: Chava
Clue: Little Chava likes big numbers.
Location: Sanubia Desert West, find the sign that says '20% off'.

#4 & 5: Alek & Aloja
Clue: Alek and Ajola play tag in the ruins of men.
Location: Sanubia Desert Central, near the ruins at the west side, look for 2 cactuars running around.

#6: Vachella
Clue: Vachella seeks the shining blue.
Location: Sanubia Desert East, investigate the Save Sphere under the tent.

#7: Robeya
Clue: O, Robeya's stuck inside.
Location: Sanubia Desert Central, in a treasure chest far to the west.

#8: Isrra
Clue: A fiery inscription--The lord of the hole is gone. Isrra thinks.
Location: Sanubia Desert West, inside one of the sand whirlpools.

#9: Elio
Clue: Much-curious Elio has left on a journey.
Location: Go back to the oasis in Sanubia Desert and take a few steps of the Save Sphere to see an event starting. After that go to the Airship's deck.

#10: Flaile
Clue: Flaile is always behind.
Location: After bringing all the other spheres it will appear automatically.

When you found one, you're challenged to a game of "Red Light, Green Light". Just get to the cactuar before time runs out without the cactuar seeing you move. If you successfully got one, you'll get their sphere. If you fail you'll get the Sphere Del Perdedor. Depending on your performance in the game you can get a price.