This achievement becomes available at the beginning of
chapter 9. You do not have to wait for post-game play. (As of this writing, I have not finished chapter 9.) The condition for unlocking the achievement is obvious from the description--defeat the adamantoise. Nevertheless, there are a few complexities that need to be addressed. In addition to figuring out how to defeat the adamantoise, you also have to figure out how and where to find it.
In Chapter 9, as soon as you check in to the Leville Station, you talk to Gentiana. She explains how you can go back to Lucis using Call Umbra. Check in at the hotel desk. In addition to resting, you have a new option--Call Umbra--use it to go back to Lucis.
Note:
Although the guide is applicable to the game as a whole, its primary emphasis is unlocking the achievement in chapter 9. As players progress through the game, there are better weapons and techniques that can be used. This is especially true since Square-Enix has provided enhanced weapons and techniques since this guide was originally written. Nevertheless, while there are better late game approaches, the manner in which the hunt is made available is the same. (Use Call Umbra to go to Lucis, talk to Cindy following a phone call, complete the
Let Sleeping Mountains Lie subquest, and finally accept the
Lonely Rumblings in Longwythe Hunt from the Hammerhead tipster, Takka.) Additionally, regardless of when the achievement is unlocked, there are post-achievement rewards as described in the final paragraph. In other words, although you may choose to use different weapons and tactics to fight the Adamantoise, you may still find the guide useful in its explanation of making the sidequest and the hunt available as well as info pertaining to pre- and post-achievement awards.
You arrive in Cape Caerm. As soon as you arrive, you get a call from Cindy. Go to Hammerhead and talk to Cindy in person. She tells you to talk to Dave (the hunter you have been collecting dog tags for if you accepted his sidequests). Dave is at the Longwythe Rest Area. Go there and talk to him. He tells you to talk to Dino inside the diner and Monica. In addition to Dino, there are other people inside the Diner. The people you have helped in quests will be in the Diner so their number varies depending on how many side quests you have completed. If you talk to them, each one will give an item. These items tend to be curatives of moderate value. There are, I believe, a total of 14 people that can appear. When you talk to Dino, Dave blocks the exit door to the Diner until you assure him you are ready to go. After you talk to Dino and the optional people you choose to converse with, tell Dave you are ready to go.
Go by foot or Chocobo and follow the quest marker to Monica. As soon as you talk to her, the Adamantoise appears. There is a timer that limits your fight to under 3 minutes after which the Adamantoise retreats into the mountain. This completes the
Let Sleeping Mountains Lie subquest and a message on a screen tells you to see Takka (Hammerhead Tipster) if you want to hunt the Adamantoise.
(Note: If you run away after the Admantoise first appears, you still get credit for the
Let Sleeping Mountains Lie subquest. However, you can get a good preview if you stand and fight. I settled on the tactics I describe below based on this short interlude. So the brief scrimmage was of value.)
Camp and eat some good food. I opted for Smoked Behemoth (+400 attack, +1K HP, & Infinite Stamina). Go to the diner in Hammerhead and select the
Lonely Rumblings in Longwythe Hunt. Then follow the quest marker on foot, by car, or by Chocobo to the Adamantoise.
The achievement unlocks when you report back to Takka after successfully completing the hunt.
You can use whatever tactics suit you best. The Adamantoise telegraphs its attacks so it's easy to defend against. If you time the parry and counter prompts correctly, there's a cool animation sequence where all four party members execute a counter-attack by jumping off the high peak onto the Adamantoise's head. (My control scheme assigned parry and counter to
and
respectively but your control scheme may differ.) The fight is more tedious than difficult. The Adamantoise has very strong defenses and has more than 50M in HP that you have to whittle down.
My recommendation is to rely primarily on Gladiolus's ImpulseTechnique. It is most effective if it is maxed out (by using it between 30-50 times) and by unlocking its limit break in the Techniques Ascension tree (at a cost of a whopping 999 AP). I equipped Gladiolus with the Force Stealer II (acquired from Tony by trading carrots) and enhanced by Cid. The Force Stealer II has an attack of 463. I also equipped Gladiolus with the best strength enhancing accessories having unlocked his third accessory slot. If you are not going to use Gladiolus's techniques, you may prefer to equip Noctis with the best accessories. I also took off Gladiolus's and Noctis's jackets to increase their strength. The meal added an additional 400 in strength so Gladiolus and Noctis were both well above 1,000 in attack strength.
The Impulse Technique requires 3 tech bars. Assuming Noctis is at level 99 [or better since a recent update increased the max level to 120] and has maxed out warp and acquired Air Dance on the Combat Ascension Tree, he can charge all three tech bars by using a Magitek Booster (acquired by fighting Imperial Forces) and executing warp attacks against the Adamantoise's eye. I used the Attack 364 Ultima Blade (acquired by having Cid enhance the Engine Blade 3 Times). However, there are a number of good choices. The Adamantoise is weakest against Long Swords so the Attack 345 Thunderbolt (found at a treasure point in Malmalam Thicket or available for purchase from the arms vendor at Leville Station) would have been good since I wanted Gladiolus to have my best long sword--the Force Stealer II mentioned above.
It is a long drop down from the eye to the ground. It may even be fatal so I made sure Noctis would never fall. If in danger, I warped out to a warp point. Ideally, though, I wanted to fully charge the 3 tech bars by executing warp attacks against the eye using the Magitek Booster for eliminating magic costs for the first few seconds. Impulse (assuming it has been equipped using the Gear menu) is executed by pressing
followed by
. Executing Impulse automatically deposits Noctis safely on the ground so he can execute it without peril even if he has just gone into stasis.
If executed optimally with the hit count in the low 30s, a level 99 Gladiolus can inflict around a quarter million HP in damage with a limit break maxed out Impulse. (This also assumes that Gladiolus's strength has been boosted with weapon, accessories, and eating an appropriate menu.) Relying almost exclusively on Impulse, it took me just under 20 minutes to defeat the Adamantoise. I didn't always execute optimally, so Gladiolus's Impulse damage ranged from just over 100,000 to about 250,000 HP. Occasionally, the Adamantoise will topple to the ground in a more vulnerable state. There is no need to change tactics. Charge the tech bar with warp attacks against the eye and execute Impulse.
These tactics will work even if Noctis is well below level 99 and if both he and Gladiolus are using weapons less powerful than the ones I used. It will just take longer and Noctis will have to rely on warp points to replenish his magic because he will not be able to fully charge the 3 tech bars in one go with the help of a Magitech booster. The party did a good job defending itself. A couple of times Ignis or Prompto got into the danger state but recovered without my intervention. If the party is below level 99, conceivably some curatives would have to be used. With the recent update, the party could be as high as level 120 which would substantially increase its lethality.
The primary disadvantage of using powerful techniques as opposed to conventional attacks, as I implied earlier, is that you need quite a lot of AP to unlock the limit break Impulse on the Techniques Ascension Tree. However, I did no special grinding. I simply accepted every single side quest and hunt as soon as they became available. By using warp attacks against the weak enemies I encountered, I got 1 AP with every kill. So, by Chap 9, I had more than enough AP to max out Gladiolus's Techniques and Noctis's Combat on the appropriate Ascension Trees.
As a final comment, I must emphasize these are just suggestions. There are many effective strategies that can be used. The Adamantoise does not heal itself so any damage, no matter how slight, counts towards its defeat. Noctis's warp attacks, in themselves, are not insignificant. So, he could bring down the Adamantoise on his own. However, Gladiolus's Impulse attacks, optimally executed, are an order of magnitude more damaging than the warp attacks. If all Impulse attacks were optimally executed, the Adamantoise could be defeated with as few as 10 Impulse attacks if that. So, although I have not done it myself, I feel the Adamantoise could be defeated with these tactics in under 10 minutes.
The time to defeat would be shorter if more powerful weapons and accessories were used. I wanted to engage during chapter 9 which limited my weapon choices. However, there are far more powerful weapons and accessories available later on in the game. One can even kill the Adamantoise instantly by casting Alterna with the Ring of the Lucii. However, players who have progressed to that extent in the game and acquired the associated skills would not need this guide to defeat the Adamantoise.
Note--"Hidden" post-achievement rewards: When you return to the Longwythe Rest Area after successfully completing the
Lonely Rumblings in Longwythe Hunt, talk to Dave who will be in front of a structure to the right of the Diner. Dave will have some comments. You will automatically find yourself back inside the Diner with all the people that were there before the
Let Sleeping Moutains Lie subquest. This time when you talk with them, each one will give you an Oracle Ascension Coin. Dave will once again block the exit until you tell him you are ready to leave. When you do so, Dave will also give you an Oracle Ascension Coin. This is potentially the largest source of Oracle Ascension Coins in the game if you have helped a large number of people up to a maximum of 14. You do not have to return immediately following the
Lonely Rumblings in Longwythe Hunt. Even if there is a long interval, Dave will be available to initiate your Oracle Ascension Coins rewards.