This Elite Mark can be obtained from Montblanc after the completion of the events at the Tomb of King Raithwall and the Shiva airship. Return to the Clan Hall and speak to Montblanc to obtain the Hunt.
The earliest and most ideal time to complete this hunt is after the events at Jahara – Land of the Garif once Larsa has rejoined your party. If the Elite Mark is attempted at this time, it is normally the highest rank Hunt that the player has attempted, making Larsa’s help a welcome addition to the team. His attacks are very strong and he can help you with healing your party when their HP drops.
The petitioner and the Mark itself can only be found during the “rainy” period in the Giza Plains. Check out the Giza Plains Rain and Dry seasons page for more information on how the weather cycle works, especially if you need to change the weather.
Travel to the southernmost portion of the Giza Plains (called the Crystal Glade) to find Nanau standing near the Save Crystal. She will provide you with a special urn which needs to be used to capture the Gil Snapper’s spirit.
No additional steps need to be completed. The “spirit” will automatically enter the urn once Gil Snapper is defeated.
The Gil Snapper is located in an area of the Giza Plains referred to as the “Tracks of the Beast”. This area will not initially appear on your map screen as it cannot be accessed just yet.
In order to gain access to the Tracks of the Beast, you must cut down six “Withered Trees” located throughout the Giza Plains. The trees will form a bridge in the southeastern portion of the map which can be used to access the zone.
There are six Withered Trees. You can find one of them in each of the following areas:
Travel to the Gizas South Bank and search the east side of the zone (just south of the wooden bridge) to find the new makeshift bridge created by the grouping of Withered Trees. You can use this bridge to enter the Tracks of the Beast.
Lastly, the Gil Snapper will only appear in the zone during heavy rains. There is a Seeq NPC named Bansat that will run towards you as you enter the zone and will tell you if the weather is right and if the beast has appeared.
He will shout “There it is! Now stand back and let Clan Centurio’s finest show you how it’s done.” Bansat will join you for this fight.
Level: 37
HP: 89,956
Steal: 1,000 gil, 2,000 gil, 4,000 gil
You may want to start off by making sure that there are no other enemies in the area around the Gil Snapper as this can be an extremely long fight. It will be made much more difficult (if not impossible) if another turtle enemy joins the fray.
Make sure to use 
Decoy and set your tank up to take a lot of damage, 
Protect, Bubble if you have it, and keep Regen on your tank as often as possible. Set up a Gambit for one of your characters to keep 
Blind and Silence on Gil Snapper as this will help to limit the amount of damage it does.
The Thunder or Thundara Magick spell (if you have it already) are extremely useful during this fight as Gil Snapper is weak to lightning-based spells. Regular attacks will do slow but steady amounts of damage due to its high defense. Take your time and keep your party healed as you slowly bring the Elite Mark down.
Bansat will tell you that he will meet you back at the Clan Hall after the Hunt is complete. Gil Snapper will also be drawn into the Urn.
Check out the video below for a (not so clean) demonstration of defeating Gil Snapper:
A video of the battle in the Zodiac Age version is included below:
Before you leave, search the area for a Green Urn that contains a key item called the “Feather of the Flock”. This item is needed to complete the Cockatrice Round-Up side quest later in the game.
Returning to the area where you found Nanau (the Crystal Glade) during the Rainy season of Giza Plains will only result in you finding a note indicating that she has left to join her tribe members and can be found during the dry season. Check the Rain and Dry in the Giza Plains section for more information on the weather patterns.
Speak to Nanau during the “dry” to receive 3,000 gil and 
Phobos Glaze.
