The Cie’th Stone for this Mission is a Cie’th Paling which blocks the way to the Titan’s Trials in the Faultwarrens. The Faultwarrens contains a number of high level Missions that you can complete towards the end of the game.
This Cie’th Stone can be found in the Haerii Archaeopolis. You can use any of the other Waystones around the Archylte Steppe to teleport to “Archylte Steppe - Haerii Archaeopolis” and the Cie’th Stone is just a few steps away up on top of the nearby pillar and into the “Way of the Ancients”. Use the map below to help you locate it:
The mark for this Mission is back out in the center of the Haerii Archaeopolis. Once you get near the area where the mark is located on the mini-map a short cinematic will play. It turns out that this battle is actually against a Tonberry which you end up facing after it “Doinks” the enemy with its knife.
Class: B
HP: 956,250
Long time fans of the series will know that, despite their small stature, Tonberrys are not to be trifled with. They are typically extremely powerful and this Tonberry is no different.
Its regular attack is called “Knife” which it will use as it runs over to one of your party members. This attack will slowly do more and more damage as the fight continues and it will also dispel positive status effects placed on a party member. Because of this, you shouldn’t spend too much time with a 
Synergist buffing your party member as this is an uphill battle that doesn’t end up being worth the time.
In addition to Knife, Tonberry will use a chain of special attacks that eventually builds up to its most powerful attack. The first three moves do nothing and are essentially Tonberry charging itself up. They are:
After “Imminent Grudge”, its next attack will be “Deep-seated Grudge”, which will inflict a very high amount of damage on your party and will fully refill Tonberry’s HP. This attack does enough damage that it will probably kill one or more of your party members.
Because this attack restores Tonberry’s HP, even if you do survive it, Tonberry’s regular “Knife” will continue doing more and more damage as the fight progresses. The fight is pretty much over after a “Deep-seated Grudge” attack and you should restart if it is used at all. The goal is to go on an all out offensive and bring the Tonberry down before its damage overwhelms you.
Get a quick 
Libra or 
Librascope out and have your 
Saboteur apply 
Deprotect and 
Deshell to greatly increase the amount of damage your chains will inflict. Getting a few buffs up from a Synergist, like 
Haste, can be helpful. The idea is to keep your party healed so as not to succumb to the damage from regular “Knife” attacks but you need to defeat the Tonberry as quickly as possible.
Hermes Sandals
Bomb Core (x7)It is recommended that this be the last Mission that you complete if you are in Chapter 11 of the game. Check out the Chapter 11 - Optional Side Quests page listed below for more information on why this is. Alternatively though, if you wish to proceed into the Faultwarrens to begin the Titan’s Trials (e.g. if you have already completed Chapter 12 and 13), use the links below.
There is also a link below if you would like to read up more on how the Titan’s Trials / Faultwarrens works:
Chapter 11: Optional Quests
Completing the remaining optional content available back in the Archylte Steppe before proceeding to the next chapter of the game.
Titan’s Trials / Faultwarrens
A subset of Missions that take place in the Faultwarrens area that involve defeating enemies spawned by the mighty Titan fal’Cie.
Full Mission List
A list of all the Missions in the game.
