The Iron Giant is the boss of the Hidden Dungeon. To unlock the hidden dungeon you must get the letter from Alus about the Star that crashed into the Ocean. The Hidden Dungeon is located in the water near the Floating Island Entrance. When looking at the map go right 2 squares until you see a dark circle in the water and go under water. You will see some Coral Reef which is the entrance.
At the end of the short walkway a short cut scene will take place and the boss will appear. The Iron Giant is one of the toughest bosses to beat and he is severely OP. He will not be beaten by normal means. Easiest way to beat requires a few things:
- This can be done with your character lvls in the late 70s but its recommended to be in the 90s. I did this at lvl 98 and had very little trouble.
-Job Lvl 90+ Bard with Apollo Harp and Madhura Harp
-Job Lvl 90+ Ninja with at least 15 Shurikens
-Job Lvl 90+ Devout with Curaja
-Job Lvl 99 Viking with 2 Shields and full Crystal gear(Job Lvl MUST be 99 for Provoke to be 100% successful)
-1 Turtle Shell
-All Party Members in the back row
You will use your Viking to Provoke the Iron Giant every round to keep him focused on one target. Meteor will hit the entire party no matter what. Once The Bard has sung its song and Turtle Shell is on the Viking, the Iron Giant Will struggle to hit him for more than 200 hp with his regular attack. Meteor still packs a decent punch.
What you will want to do is use the Bard's sing ability with the Madhura harp so that Protect is casted on the entire party for 2 turns. On the next turn you will swap the harp with the Apollo Harp and use Sing as well. Rinse and repeat to keep both active.
With your Devout you will use Curaja every round on the entire party to ensure you are all at full health, you will be able to get away Curaga some rounds but try to avoid it just to be safe, especially later in the fight.
The Ninja will be used to use Turtle Shell on the Viking for additional protection. If any items need to be used, the Ninja will be the one to use the item on their turn. I really only needed Turtle Shell though. After that, just throw Shurikens at the Iron Giant. You should hit for 9999 which if you havent already figured out is the max damage that will be displayed however you will be doing much more Damage.
The Battle starts off pretty timid. Bard Sings, Viking Provokes, Ninja throws, Iron Giant attacks and the Devout Heals. As mentioned before the damage will be limited substantially by the Bards song and Turtle Shell. Once his Health drops to about 25-35% instead of Meteor he will use Swipe which hits for about 4k. This is when Curaja is 100% necessary on the whole party.
As long as you keep the songs coming and keep healing every round, your Ninja should dispatch the Giant with little resistance. It will take some time though.